as figured by Lacaze-Duthiers nor the slightest signs of movement. 

 Lacaze-Duthiers, in his remarkable "Memoir of Dentalium," in the 

 "Annals des Sciences Naturelle," has given an exhaustive description 

 of the organization and development of Dentalium. Relations are 

 pointed out showing that its affinities are with the lamellibranchs, 

 gasteropods and other larger and smaller groups of mollusks and 

 annilids. Some years ago in the "Proceedings of the Boston Society of 

 Natural History" I called attention to some curious resemblances 

 that Dentalium held to the Tetr abranchiate cephalopods, namely the 

 long retractile, thread-like tentacles, the curious cartilagenous body 

 surrounding the oesophagus and the fact that the long shelly tube 

 curves dorsally as in Nautilus, Ammonite and other members of the 

 class. 



kCMJEk TESTUDINALIS IMuller 

 PI. I. Fig. 2. Length 20mm. 



Head broad, tentacles long, wide apart, eyes at base of tentacles 

 which are slightly thickened, mouth large, encircled by a membrane 

 which is very mobile and strongly foliated. In the "Proceedings of 

 the Boston Society of Natural History," (Vol. XXXIV, No. 8) I have 

 described the early stages of this species. I found no trace in the 

 embryonic form of a helicoid shell. Fig. 2 (A) shows attitude of the 

 head; (B), highly enlarged view of tentacle; (C), mouth showing 

 radula within. 



ACMiEA ALVEUS Conrad 

 PI. I. Fig. 3. Length 14 mm. 



In motion the head swings freely to the right and left, protruding 

 beyond the edge of the shell, as in Fig. 3, (A). Tentacles long and 

 wide apart. Fig. 3, (B) another view of head. 



CREPIDULA FORNICATA Linn 

 PI. n. Fig. 4. Length 38 mm. 



Head bi-lobed, deeply cleft, lobes long and oval; tentacles thick, 

 not pointed, eyes on thickened base; foot oval, anterior face rounded 



