ACEPHALA NUUA. Ill 



the Acephah with tube* is found in tin- fact that tin TO is a double 

 projection on OIK- jmrt of the cone, which really n- cnihlr.s tin- two 

 valves of the Ac.-jiliala. The aflinity l> t\vrm these little tubes and 

 those which envelope the tentacula of certain Tcrebella, formerly 

 canned this animal to be ret'envd to tin- .\nm-li . 



The speeie* most known, Asper. javanum, Mart., Conch.. 1 

 jl. 1, f 7, is seven or eight inches in length*. 



ORDER II. 



ACEPHALA NUDA f. 



The naked Acephala (a) are not numerous, and are sufficiently 

 removed from the ordinary Acephala, to form a distinct class, were 

 such a division considered requisite. Their branchiae assume varimi> 

 fon UN. I nt are never divided into four leaflets; the shell is replaced 

 by a cartilaginous substance which is sometimes so thin that it is as 

 llexible as a membrane. We divide them into two families. 



FAMILY I. 



SEGREGATA(6). 



This family comprises those genera in which the individuals 

 that compose them are insulated and without any mutual organic 

 connection, although frequently living in society. In the 



HIPHORA, Brug. THALIA, Drown. SALPA, and DAGYSA, 



Umclin, 



The mantle and its cartilaginous envelope are oval or cylindrical, and 

 open at the two extremities. Near the anus, the opening is trans- 

 verse, wide, and furnished with a valve which permits the entrance 

 of water, but not its exit ; near the mouth, it is simply tubular. Mus- 



* Add the Arrosoir a manchettes, Savig., Egyp. Coq. pi. xiv, f. 9. 



t since called by M. De Blainville ACEPHALUPHORA HETKUOBRANCHIATA. As 

 to Lamarck, he makes a separate class of them, which he calls the TUNICATA, and 

 \\liidi he places between his Radiata and his Permes ; but these animals having a 

 bruin, nerves, a heart, vessels, liver, &c. this arrangement is inadmissible. 



0^ (a) Or the Acephalcs sans coquillfs of our author. ENO. ED. 



(I) As this family has received no name from our author, we have been com- 

 pelled iu conformity with the plan adopted from the commencement of the work, 

 t<> n imdy the omission, for such we consider it, by the above word ; in the selection 

 of uhuh we have been governed by that which the Baron himself affixes to the 

 second family, or hi- Ayyreyh. ENO. ED. 



