74 



A. K y err ill — The OpisthoteuthidcB. 









Table 



11. 









CaCOg 



BaOaHa 



BaOaHa 



COa 



Error 



Corrected 





taken 



taken 



found 



found 



on CO2 



Error 





grm. 



grm. 



grm. 



grm. 



grms. 



grm. 



1. 



•5023 



1-1385 



•2851 



•2190 



•0020 — 



•0000 



2. 



•5056 



1-1414 



•2801 



•2211 



•0014— 



•0006 + 



3. 



I'OOll 



2-0712 



•3704 



•4367 



•0038- 



•0002 J- 



4. 



1-0030 



1-8788 



•1736 



•4376 



•0037- 



•0003 + 



The calcium carbonate used in this test of the smaller appar- 

 atus was the purest commercial article available ; the error 

 applied as a correction in the last column (•0040 grm. on car- 

 bon dioxide for a gram of carbonate) was determined by five 

 closely agreeing analyses of various amounts in the larger 

 apparatus. 



The process, beside being delicate, is fairly rapid — the aver- 

 age time for a determination being about three-quarters of an 

 hour. 



It only remains to thank Prof. F. A. Gooch for many help- 

 ful suggestions and kindly advice in this investigation. 



Art. XI. — The OjpisthoteuthidcB. A Remarhahle New 

 Family of Deep Sea Cephalopoda^ with remar'ks on some 

 points in Molluscan Morphology /* by A. E. Yerrill. 



The genus Opisthoteuthis was first described and illustrated 

 by me from a species {0. Agassizii) dredged by Mr. A. Agas- 

 siz, on the " Blake Expedition" off Grenada, in 291 fathoms.f 



A second, but more imperfect, specimen was dredged by the 

 Albatross, in 1884, off ]^ew Jersey, in 1058 fathoms.;): 



The most remarkable external features of the genus are the 

 posterior position of the siphon, which is also directed backward, 

 and the close union of the pedal web with the entire under sur- 

 face of the body. Thus the eight arms together with the broad 

 web, which extends nearly to their tips, form an extensive disk- 

 like ventral foot, adnate to the inferior or ventral surface of the 

 body and extending beyond it on all sides. (Figures 1, 2, 3.) This 

 arrangement is analogous to the position of the foot in the lim- 

 pets and chitons among Gastropoda. Like those forms, Opis- 

 thoteuthis must be essentially a creeping and clinging mollusk, 

 though not exclusively so, for the presence of small lateral 

 fins indicates that it can swim, more or less. The siphon 

 appears to be too small to be used for efficient locomotion. 



The adhesion of the arms and web to the body must prevent 



* Abstract of a paper read before the National Academy of Science at Wash- 

 ington, D. C, April, 1896. 



f Bulletin Mus. Comp. Zoology, vol. xi, p. 113, plates I and II, 1883. 

 X Trans. Conn. Acad. Sci., vol. vi, p. 408. 



