vot,. XVI 

 I8!):t. 



] PROCEEDINGS f)F THE NATIONAL MUSEUM. 4fil 



tiinied nppcimost, as avIicii occiipiecl by the living animal. <i is in 

 each case tlu' outline- fioiii (lie vcntial face and /> from the side, 

 while Fi^'. «'^ re|)iesents the s[)ecics Liiiiacina infidta. 



The i'ei)rcsentatives of the j^cnus Clio are j>iven u]»on I'late III. Of 

 these the one sjxM'ies rininla ( I'^i^is. 9 and 10) was not taken upon this trip 

 of Ihc Alhdfross, but Ix'lon^^s fartlier north, haxinj;' been taken abun- 

 dantly by tlic l^'ish Commission Scliooner (hampus in In^r investigations 

 of the (Inir Stream, southeast from Marthas Vineyard, at the surface 

 in the summer of l.S(S<). Two foiuis of it were found — the si)ecies 

 vir<iul<i proi)er (rei)resen<e<l in y\^. D) tVom lateral view, also an ojjtical 

 section ironi front, showiujc^ its circular shape, and a variety of the 

 sanWjCorniJoriHis, Avhieli differs from tlie former only in the lengtli of 

 tlu' shell, the size of its openiii};' and tlie <;urve of the posterior i»oint 

 being- relatively about the same. 



The one otlier ptcropod taken with shell (j[uit(; unsculptured and of 

 circular section is Clio (Cresein) conica, re])resented in Fig. 11, which 

 thus shows its straightness in all jxtsitions, its great length, and slen- 

 dernesa also as comi)ared with ajiy of the others, in Fig. lU is rejn^e- 

 sented Clio {Sfi/liola) mibuiata, which is distinguislied from the other 

 straight- shelled pteropods by the ])ossession of a dorsal longitudiiuil 

 groove which runs somewhat obliquely along the shell out into a pro- 

 jection, which on its account better resists fracture perhai)S, or else is a 

 normal feature of the shell. This groove gives a very evident asym- 

 metry to the shell — as if it wt-re (he axis of the animal and the poste- 

 rior part of the shell were bent away from this axis. 



In the optical section the groove- is sec^n to b(i caused by a folding 

 up of a ridge of the shell; there is also to be noticed s(nne dorso ven- 

 tral flattening of the aniirial. Whether this groove beais any relation 

 to any anatomical i)eculiaritics of the animal, I have, as yet, not 

 as(;ertained. 



The course of longitudinal groove is representcMl by the dotted lines 

 in the figure. The three other si)ecies of Clio represented have cer- 

 tain i^eculiarities comnntn to all, and in a Avay they stand in a series. 

 Thus in Fig. 13 are given outline drawings of two fragments of Clio 

 {llynlocylix) striata, showing' an individual variation in si/e, a being a 

 small and b one of the largest sjx'cimens; for although quite a 

 large vial full of the mollusks was taken at one of the surface sta- 

 tions, it was very difficult to get very nuiny of the shells, and none 

 I)erfect; they, being* so delicate and covering loosely only the posterior 

 ])art of the aninuil, are easily detached and lost in collecting. The 

 side views given in a aiul h of Fig. 13 show how the outline of the 

 shell is thrown into a series of transverse grooves shown here in the 

 profile of the figure, while the view into tlui anterior end of the shell 

 gives a dorso-ventrally flattened opti<%il section, as indicated in r. In 

 Fig, 14 {a lateral of the i)osterior part oidy, h ventral, and c frontal 

 view of Clio (.v. str.) balantiuni) the same features are emphasized as far 



