118 mollusca. 



Okbicula, Cuv. 



The Orbiculae have two unequal valves, one ofj which, that is round 

 and conical, when viewed by itself, resembles the shell of a Pa- 

 tella; the other is flat and fixed to a rock. The arms of the animal, 

 — Criopus, Poli, — are ciliated and spirally recurved like that of the 

 Lingulee. 



The seas of Europe produce a small species. Patella anomala, 

 Mull., Zool. Dan. V, 26; Anomia turbinata, Poli, XXX, 15; 

 Bret. Sowerb., Lin. Trans., XIII, pi. xxvi, f. 1. 



The Discing, Lam., are Orbiculse, the inferior valve of which is 

 marked by a fissure. The 



Crania, Briuj. 



Should be approximated to the Orbiculae. The arms of the animal 

 are also ciliated, but the shells have deep and round internal muscu- 

 lar impressions, that have caused it to be compared to the figure of 

 a skull. 



One of them inhabits European seas ; Aiiomia craniolaris, L. ; 

 or Crania personata, Bret. Sowerb., Lin. Trans., XIII, pi. xxv, 

 f. 3. Several are fossil ; such as the Cran. antiqua, and the 

 others of which M. Hceninghaus has given an excellent Mono- 

 graph. 



CLASS VI 



CIRRHOPODA *. 



[Lepas and Triton, Lin.'\ 



The Cirrhopoda, in several points of view, are intermediate between 

 this division and that of the Articulata. Enveloped by a mantle, and 

 testaceous pieces which frequently resemble those seen in several of 

 the Acephala, their mouths are furnished with lateral jaws, and the 

 abdomen with filaments named cirri, arranged in pairs, composed of 

 a multitude of little ciliated articulations, and corresponding to a sort 

 of feet or fins similar to those observed under the tail of several of the 

 Crustacea. Their heart is situated in the dorsal region, and the 

 branchiae on the sides ; the nervous system forms a series of ganglions 



* M. De Lamarck has changed this name into Cirripeda, making it a class. 

 M. de BlainvUle also makes a class of them, but he changes the name to Nemato- 

 PODA, and places them with the Chitones, in what he caUs his type of the Malen- 



TOZARIA. 



