80 CONTRIBUTIONS 



the umbones ; substance of the shell thick ; lunule none ; 

 beaks elevated, recurved; anterior series of teeth short 

 posterior series long ; fosset small and oblique ; cavity of 

 the shell rather deep ; margin very minutely crenulate ; 

 nacre very pearly. 

 Diam. .4, Length .6, Breadth .8, of an inch. 



Observations. Resembles Gobboldice and Icevigata (Sow- 

 erby) . It differs from the first in being smooth from the last 

 in not being truncate, and from both in having a crenulated 

 margin. It has perhaps a stronger resemblance to the mar- 

 garitacea of Lamarck, a recent European species, and the 

 only recent one known to be crenulate. That distinguished 

 naturalist says it is found fossil in various parts of France. 

 It appears to me that our shell differs in being more 

 robust, more transverse, and having less pointed teeth. 



In fine specimens of the Sedgewickii, with the aid of the 

 microscope, minute diverging lines may be observed. 



In attaching the name of a distinguished geologist to 

 this species, I must make my acknowledgements for the 

 instruction and pleasure derived from his eminently useful 

 labours. 



JV. ovula. Plate 3. Fig. 59. 



Description. Shell ovate, oblique, inflated, very inequi- 

 lateral, transversely striate, longitudinally and very mi- 

 nutely ribbed ; substance of the shell thin ; lunule large, 

 not deeply impressed ; beaks pointed, recurved ; anterior 

 series of teeth short posterior series long ; fosset nearly 



