CEPHALOPODA OF THE HAWAIIAN ISLANDS. 28 1 



Subfamily TREMOCTOPODIN2E. 



Philonexidce H. and A. Adams 1858. vol. 1, p. 21. 

 Tremoctopidce Tryon 1879, p. 130. 

 Trenwctopodidce P. Fischer 1882. p. 334. 

 Tremoctopodirue Berry 1912b, p. 386. 



Adult small. Third left arm of the male hectocotylized ; its outer surface ornamented with fringe- 

 like papilla;. Dorsal arms of female connected at base by a broad veliform membrane, which extends 

 along their margins, leaving only the very attenuate and frequently decollated extremities free. Re- 

 maining arms webbed only at the base, their suckers larger and better developed than those of the dorsal 

 pair. No calcareous egg case or shell. Two large aquiferous pores on the dorsal aspect of the head and 

 a smaller one at either side ventrally jus"t in front of the funnel. Mantle articulating with the funnel 

 by membranous folds; no definite locking cartilages. Funnel organ poorly developed and represented 

 only by a series of longitudinal lamellse. 



Genus TREMOCTOPUS Delle Chiaje 1829. 



Tremoctopus Delle Chiaje 1829, T. 70, 71 {fide Wiilker). 

 Octopus {Philonexis) d'Orbigny 1335, p. 14. 

 Philonexis d'Orbigny 1845. p. 200. 

 Tremoctopus Naef 1912b, p. 199. 



Since only the single genus of the group is known, its characters are entirely those of the subfamily. 

 Type. — Tremoctopus violaceus Delle Chiaje 1829 (monotypic), a species originally described from 

 the Mediterranean. 



Tremoctopus violaceus Delle Chiaje 1S29. (PI. xux, fig. 3, 4.) 



? Tremoctopus violaceus Delle Chiaje 1829, T. 70, 71 {fide Wiilker). 



Octopus gracilis Souleyet in Eydoux and Souleyet 1852, p. 13, pi. 1, rigs. 8-9. 



? Octopus dubius Souleyet in Eydoux and Souleyet 1852, p. 15, pi. 1, figs. 10-14. 



? Tremoctopus dubius Tryon 1879, p. 131, pi. 43, fig. 80, 81 (after Souleyet). 



Tremoctopus gracilis Tryon 1S79, p. 131, pi. 43, fig. 82, 83 (after Souleyet). 



Tremoctopus quoyanus Hoyle 1904, p. 12, fig. A. 



Tremoctopus sp. (near quoyanus d'Orbigny) Berry 1909, p. 418 (locality record only). 



Animal small, pelagic. The sexes are so conspicuously dimorphic that a separate description is 

 necessary. 



Female: Mantle short; width about equal to length; pouch-shaped, widest anteriorly, and either 

 simply rounded behind or rapidly narrowing to a rounded point; a sharp median longitudinal groove 

 on the ventral surface indicates the position of the median septum of the mantle cavity. Mantle opening 

 very wide and full, extending to a point just above the center of the eye on either side, but well behind 

 it; mantle of scanty extent below, so that its margin barely meets the posterior edge of the funnel. 



Head large, flattened; extremely short and broad, the large prominent rounded eyes rendering it 

 usually wider than the body. Eyes not at all pedunculated. Entire surface covered by a loose 

 smooth delicate skin or cuticle of hyaline consistency and unpigmented, which is perforated by four 

 small oval openings — the so-called aquiferous pores — a pair on the dorsal aspect being situated one at 

 the base of each dorsal arm just a little outside the axis of the latter, and another pair about half as large 

 situated one at the base of each ventral arm at either side of the tip of the funnel. Funnel large, 

 compressed, very broad at the base, its outline almost that of an equilateral triangle; only the narrow 

 apex free. Funnel organ composed of a number of longitudinal lamellae or folds, terminated near the 

 apex by a small acutely pointed valve-like flap. (PI. xux, fig. 4.) The base of the funnel just over 

 the retractor muscles articulates with pocket-like grooves on the inner surface of the mantle by means 

 of a thickened and recurved fold of the posterior margin. 



Arms (pi. xux, fig. 3) slender, graceful; decidedly unequal, order of length 1, 2, 4, 3; dorsal arms 

 decidedly longest and when perfect terminating distally in a very long delicate thread-like process ; second 

 arm pair a little shorter than the first, notably stouter, wider and less attenuate ; third arms decidedly 



