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. Sphjerulites. 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 uniigured 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. 



