SHELLS. 215 



on each side before, with the anterior margin crene- 

 lated, front slightly advanced, tridentate, arms wartyj 

 length five inches. 



The fifth section {Trigona) have the carapax gene- 

 rally triangular or subovoid, with the anterior extre- 

 mity narrowed and pointed, ordinarily very rough 

 and uneven, with the eyes lateral ; claws often larger 

 in the males than in the females. Many of these 

 crabs are commonly called Sea Spiders. 



In this section we find the genus Maia. The 

 animals of this genus . live on rocky or muddy shores 

 around Bermuda, and conceal themselves among 

 fluci. The type of this genus is the Maia squinado. 



Another species common to Bermuda is the Hyas 

 araneus, belonging to the genus Hyas. 



The sixth section comprise the Cryptopoda. A 

 few species of the animals of this section withdraw 

 their feet within the vaulted margin of the shell 

 when at rest, with the exception of the large claws. 

 Belonging to this section we find the genus Calapa, 

 Of this genus we find only one representative around 

 our shores — the Calapa granulata. 



The seventh and last section — the Notopoda — is 

 formed of crabs having the two or four posterior 

 feet inserted on the back, or above the line of the 

 others. In the Notopada we find the genus Ranina . 



