250 SALPACEA. 



RUDISTES. Lam. A family of the order Conchifera Mono- 

 myaria, Lam. the shells of which are described as irregular, very 

 inequivalve, without distinct umbones ; the ligament, hinge and 

 animal entirely unknown. The shells contained in this family 

 may be thus distinguished. 



1. Calceola. Large valve conical ; attached by a flat space 



between the umbones, which form the extremities of the 

 shell. Fig. 194. 



2. Hippurites. Large valve cylindrical, with two internal 



lobes or varices. Fig. 198. 



3. Sph^erulites. Large valve attached, including Radiolites. 



Birostrites is proved to be the cast of a Sphserulites. Fig. 

 193, 196. 



4. Hipponyx. Flat valve attached, upper valve conical. Fig. 



199, 200. 



RUDISTES. Bl. The second order of the class Acephalophora, 

 Bl. containing the genera Sphserulites, Crania, Hippurites, Radio- 

 lites, Birostrites and Calceola. 



RUDOLPHUS. Lam. Monoceros, Auct. 



RUFOUS. Reddish brown. 



RUGOSE. Rough, rugged. 



RUPELLARIA. Fl. de Belvue. An unfigured shell placed by De 

 Blainville in a division of the genus Venerirupis. 



RUPICOLA. Fl. de Belvue. A shell described by De Blainville as 

 an equivalve, terebrating species of Anatina. A. rupicola, Lam. 



SABINEA. A genus of shells resembling small species of Littorina, 

 as L. Ulvse, &c. of our shores. 



SADDLE OYSTER. Placuna Sella, so called on account of a 

 resemblance in shape to a saddle ; the part near the umbones 

 being flat, and the ventral margins being turned up in a sort of 

 fluting or peak. 



SAGITTA. (An arrow.) An ancient name for Belemnites. 



SALIENT. (Saliens.) Jutting out, prominent. 



SALPACEA. Bl. The second family of the order Heterobran- 

 chiata, Bl. containing no genera of shells. 



