PLATE XXVII, 



Fio-. 345. Heterofusiis retroversus ; from an original drawing by Mr. Alex. 



Agassiz. 



h. heart, d. c. digestive cavity. op. operculum. vi. mouth. a. anus. 

 ov. ovary. s. siphon. w. wings. t. tentacle, ot. otolite. 



Fig. 346. The same, at rest on the bottom of the jar. 



Fi<i-. 347. The same, in rapid motion ; the natural position of thi.s figure is sacri- 

 ficeid to the exigencies of the plate, the shell should be much less ob- 

 liquely poised, and the upper arm should be nearly horizontal. 



Fig. 348. The same, floating with expanded arms, as seen from the top of the 



jar, when the animal is in captivity. 

 Fio-. 349. Heterofusiis balea. The shell, copied from Dr. Stimpson's figure 



of Spirialis Qouldii. 



