HIGHER CRUSTACEA OF NEW YORK CITY 149 



Family 

 Pinnotheres ostreum Say 

 Oyster crab 



Pinnotheres ostreum Say, T. Acad. Nat. Sci. Phila. Jour. 1817. 

 1:67, pU, fig.s. DeKay. /. c. 1843. p.i2, pl.7, fig.i6. Verrill. /. c. 1874. 

 p.546 (figure given is P. maculatum). 



Carapace rounded, that of female soft and thin, eyes small. 

 Female found only in branchial cavity of oyster. 



The members of this genus are noteworthy in that the females 

 live within the branchial cavity of certain lamellibranch mollusks, 

 the present species inhabiting the oyster, while an allied form, 

 P. maculatum, lives in the common mussel. The males are 

 free. 



These crabs were originally known as Pinnoteres, " the guardian 

 of the Pinna," for an allied species in Europe lives in the shell of 

 a lamellibranch, Pinna, and was supposed to give warning to the 

 mollusk at the approach of any danger, so that it could close its 

 shell. 



The oyster crab is of some economic importance as food, but the 

 difficulty of obtaining a sufficient supply limits its use. 



Order 4 STON1ATOFODA 



Malacostraca with a small carapace which does not cover the last 

 three thoracic segments. The abdomen is proportionally very large, 

 and its first five appendages bear gill filaments. The first five 

 thoracic appendages are maxillipeds, and the last three are small 

 biramous legs. Eyes stalked. 



A very small order with only one representative on our coast. 



Squilla empusa Say 



Mantis shrimp 



Squilla empusa Say, T. /. c. 1818. 1 1250. DeKay. /. c. 1844. p.32, 

 pl.i3, fig.54- Verrill. /. c. 1874. p.55i. 



A large form, which, besides the characters of the order, shows 

 the following : Antennulae with three flagella, antennae shorter, with 

 a large scale. The second maxillipeds large and subchelate, the 



