[Jordan and Evermann, 1896-1900, p. 2729 (young as Mancalias uranoscopus Murray); p. 2730 (young as Mancalias shufeldti [Gill]); Barbour and Bigelow, Proc. New England Zool. Club, vol. 23, 1944, p. 16 (adult, as Reganichthys giganteus, new genus and species); Clarke, Discovery Rept., vol. 26, 1950, p. 1 (adult).]
This deep sea angler is so bizarre in its appearance that there is no danger of confusing it with any other Gulf of Maine fish, unless it were with some other member of its own family. In the large female, the body is strongly flattened sidewise; the eyes are very small and set high on the head; and the mouth is nearly vertical when it is closed. Perhaps their most striking external feature is the very long and extremely slender bristlelike spine or "tentacle," that is borne on the top of the head. This is jointed about two-thirds the way out along its length, and it ends in a fleshly, pear-shaped swelling ("illicium"), the tip of which is described as pierced by a small pore. The illicium is supposed to be luminous, and it bears 2 to 4 short filaments. This head tentacle corresponds to the whiplike head spine of the goosefish, but is situated farther back, about abreast of the eyes. It is interpreted as representing a vestige of the first dorsal fin. The basal [page 544] joint of the head tentacle is provided with retractor muscles by which it can be withdrawn rearward into a tunnel-like sheath along the head and back, bringing the "bait" close to the mouth.
Bertelsen has found (from dissecting a West Greenland specimen) that when this happens, the rear part of the hard axis of the head tentacle, which is enclosed in the very elastic skin, emerges from the back of the fish, about midway between the caudal fin and the base of the pectoral fins, so as to form the axis of a slender, tapering "dorsal tentacle." Thus this extraordinary and unique structure, which has been the subject of much discussion, is actually the rear end of the head tentacle which protrudes when the latter is drawn rearward.
When the cephalic tentacle is moved forward by its protractor muscles, its protruding rear end is withdrawn into the tentacular sheath, either partially, when the so-called dorsal "tentacle" appears as a short fingerlike process, or wholly, leaving simply an indentation or pore in the midline of the back, as it is in the Gulf of Maine specimen pictured in figure 288.
Close behind the so-called "dorsal tentacle" (or behind the pore representing the latter) are a pair of low, fleshy appendages or "caruncles," scarcely noticeable on large specimens, but more conspicuous on small. These have been interpreted as vestiges of the first dorsal fin, for each of them encloses a spine that can be felt if not seen. Their function is not known.
The skin is strewn with small prickles on very small specimens, but is close-set with low conical, broad-based thorns on larger fish. The eyes are minute, seemingly functional on small fish, but covered over by skin and apparently blind on large ones. The gill slits are very small, C-shaped; placed below the pectorals and a little behind them. The small, slender, sharp-pointed teeth are directed into the mouth. The dorsal and anal fins each have 4 rays, thick, fleshy, and tapering, as the caudal rays are also. The central caudal rays are forked. The caudal fin has been described as occupying as much as two-fifths of the total length of the fish when it is intact. But it has been much damaged in most of the specimens that have been seen, and the membranes of all the fins have been mostly torn away.
Small ones are jet black, but the dermal prickles, being colorless, show white against the black skin on large specimens, giving a granulated black and white appearance.
The parasitic males are fastened to the ventral side of the female, by two outgrowths from the front of the head, that are fused at the tip. They have no teeth, no tentacle-like spine and no eyes, and the alimentary canal is vestigial; in fact, about the only important internal organ is a large testis. But their fins resemble those of their mates, as do the gill openings; their skins are prickly; and they are similarly black. Those that have been seen (1 or 2 per female) have ranged from about 33/8 inches (85 mm.) long to about 6 inches (150 mm.) long (Gulf of Maine specimen).
Oceanic and apparently cosmopolitan, for adults have been reported from Greenland; Iceland (where it has been taken the most often); off Nova Scotia; Gulf of Maine; near the Azores; and in the sub-Antarctic. Young specimens apparently referable to this species are reported off southern New England; from the Caribbean; near the Canaries; north of the Cape Verde Islands; from the South Atlantic (lat. 52°25' S., long. 9°50' E.); and also widespread in Indo-Pacific waters.
A female, about 32 inches long to the base of the caudal fin, and about 40 inches counting what remained of the latter (fig. 288), with one male attached, and showing the scar of attachment of another, was taken 12 miles south of Mount Desert rock, at 125 [page 545] fathoms, in October 1943, by the schooner Dorothy and Ethel II, Capt. Harold Paulsen. A second female, about 187/8 inches long to the base of the caudal fin, and about 243/8 inches counting what was left of the caudal fin, trawled on the southeast part of Georges Bank, between 150 and 200 fathoms, in February 1927, appears to belong to this same species. A third probable Gulf of Maine record is of a fish, about 3 feet long, and weighing about 20 pounds, that was taken by the trawler Ebb, in 140 fathoms, on Georges Bank, in June 1936. Photographs of it appeared in the Boston Globe and in the Boston Post for June 29 of that year.
 So described by Clarke (Discovery Rept., vol. 26, 1950, p. 9) for an Antarctic specimen; the pore is not visible on the specimen we have examined.
 Dahlgren (Science, vol. 68, 1928, p. 65) describes the tip of the illicium of an unnamed species of Ceratias as with an open gland in which light is produced by bacteria.
 Four in the Gulf of Maine specimen described by Barbour and Bigelow (Proc. New England Zool. Club, vol. 33, 1944, p. 9) as Reganichthys giganteus; two (each bifid) in an Antarctic specimen described by Clarke.
 Vid. Meddel. Dansk Naturh. Foren., vol. 107, 1943, pp. 190-193; see especially his fig. 4, p. 192.
 See Regan and Trewavas (Rept. 2, Danish Dana Exped. (1928-1930), 1932, pp. 23-24) for an account of the lateral line papillae in different families of deep sea anglers.
 This was the case in the specimen about 47 inches (119 cm.) long described by Kröyer (Naturhist, Tiddsskr., Ser. 2, vol. 1, 1844, pp. 640-642); also in one pictured by Goode and Bean (Smithsonian Contrib. Knowl., vol. 31, 1895, pl. 117, fig. 399, after Gaimard).
 Kröyer's original specimen from Greenland.
 See Clarke (Discovery Rept., Vol. 26, 1950, p. 14, table 1), for measurements of several specimens.
 For complete list of localities for adults and young, see Clarke, Discovery Rept., Vol. 26, 1950, pp. 23, 30.
 This specimen, now in the Museum of Comparative Zoology, was described by Barbour and Bigelow (Proc. New England Zool. Club, vol. 23, 1944. p. 9) as "Reganichthys giganteus."
 This specimen, now in the Mus. Comp. Zool., and first described by Parr (Bull. 63, Boston Soc. Nat. Hist., 1932, pp. 12-13) as Mancalias uranoscopus, was later made the basis of a new genus, Typhloceratias, by Barbour (Proc. New England Zool. Club, vol. 21, 1940, p. 78). Its head and back have been so badly damaged that it has lost whatever tentacular structures it may have had originally.