QUESTIONS ON BIVALVES. 191 



PINNA Pectinate* 

 SPINY SEA WING. 



Specific character. Shell triangular, oblong, 

 with about eleven longitudinal ribs, having con- 

 cave spines, which increase in size as they 

 approach the broadest end ; the other side des- 

 titute of ribs, but obliquely striated up to the 

 ribs ; shell thin, pellucid, brittle, of a light brown 

 colour, darker towards the beaks; inside of a 

 pearly hue ; breadth three inches at the gaping 

 end, which is slightly rounded ; length six inches 

 and a half. 



This shell inhabits India ; it has also been 

 found on the coasts of Dorset and Sussex. 



QUESTIONS ON THE BIVALVE 

 SHELLS. 



1 . Describe the part of a Bivalve shell which 

 unites the two valves. 



2. By what means are the animals able to 

 open these valves 1 



3. What is the meaning of the terms equi- 



* Plate X. figure 4. 



