MUSEUM OF COMPARATIVE ZOOLOGY. 287 



produced beyond the shell." Troschel states (Gehiss der Sehnecken, I. p. 1G1, 

 1863) that the external mouth parts exhibit "ein vorstehender nissellbrmiger 

 Theil " which cannot be retracted and extended, and is not a true proboscis. 

 He compares it to an elongated lower lip, and states that it is fissured on the 

 upper side lengthways with a deep incision. Lastly, Gray, in Mrs. Gray's Fig- 

 ures of Molluscous Animals (Vol. III. pi. cclxviii. figs. 12 a, 12 b, from a manu- 

 script sketch by Curtis, cf. Vol. IV. p. 83, 1859), shows a long slender pointed 

 proboscis or tubular unforked organ, protruding from between the tentacles to 

 a distance equal to the whole length of the animal behind the head. Troschel 

 could find no jaws; another authority states that the jaws are rudimentary. 



A small specimen of C. hunyaricus, taken by the Fish Commission off 

 Martha's Vineyard in 458 fms., has a bilobed muzzle so short and retracted 

 by the alcohol as to be hardly more than a gash in the median line between 

 the tentacles. The figures given by Jeffreys, Forbes and Hanley, etc., which 

 have been copied by Tryon and others, show a moderately extended bilobed 

 muzzle, in no respect resembling Curtis's sketch. What is the explanation of 

 these discrepancies 1 Simply that, in opposition to the old statements, by 

 whomsoever made, this animal has a long retractile proboscis, which can be 

 completely exserted so that it shows no line of division between it and the 

 head; this is pulled in by the tip, and when nearly retracted its sides near the 

 base resemble a muzzle vertically cleft, as there is on each side under the skin 

 a sort of nearly cartilaginous buttress more solid than the proboscis, and which 

 projects when the latter is withdrawn. These buttresses, however, contract 

 strongly in alcohol, and then of the oral aperture only a vertical slit is visible 

 between the tentacles. In the Rhacbiglossa the proboscis is pulled in by the 

 base, in this group retracted by the tip; in Cyprcea it is usually rather short, 

 in Capulus it is very long, its distal half split on the upper side, so that it can 

 be expanded into a sort of plaque, which, I imagine, in life could envelop any 

 Bmall soft thing, so that the Capulus could smother it and suck up its juices at 

 leisure, much as a starfish envelops a young oyster by projecting the mem- 

 branes of its stomach out of its mouth and about the victim. 



I regard the group as forming a family with the following characters: — 



Shell patelliform, without internal processes ; the nucleus spiral, posteriorly 

 directed; the muscular impression horseshoe-shaped; the mentum prolonged 

 for use as an oviphorus; the gill composed of laminae, each basally attached to 

 the under side of the dome of the mantle over the head and proceeding from 

 left to right; the proboscis long, retractile from the tip, split above and ex- 

 panded at the distal extremity; foot not secreting any shelly base; young 

 undergoing all larval changes within the ovioapsule. 



In regard to the species mentioned in Tryon's Monograph of the group, it 

 may be added that Hipponyx Danieli Crosse is almost certainly Patella calyptra 

 of Martyn, described in the last century. A magnificent specimen from the 

 Fiji Islands is in the National Museum. It is a Capulus, and not a Hipponyx. 

 Hipponyx crystallinus (Gould) Tryon is a Thyca, and should be transferred to 

 Capulus, where Gould originally placed it. It lives parasitic on starfishes. 



