74 REPORT OF COMMISSIONERS OF INLAND FISHERIES. 



Pinnotheres ostreum Say. " Oyster Crab." 



Plate II. Figure 6. 

 P. ostreum Say. Verrill and Smith, 1874. 



The carapace of the female is thin and membranaceous. The 

 surface is smooth and shining. In color it is white, tinged with pink. 

 The males, which are smaller than the females, are brown with a 

 central dorsal stripe. 



Habitat: female in the gill chamber of the oyster; the male free- 

 swimming at the surface. 



Distribution: Cape Cod to Florida. 



Economic value: edible. 



Season in Rhode Island: 



When are the eggs laid, and how long after copulation? 



How long does the female carry the eggs? 



Extent of hatching season: 



LARVAL FORMS. 



The first zoea, as figured by Birge (" On the First Zoea Stage of Pin- 

 notheres ostrem" by E. A. Birge, Am. Nat. Vol. XVI, p . 589-591,) differs 

 from other Brachyura in the absence of the dorsal and lateral spines. 

 Conn. ("Larval Skin of Decapods" by H. W. Conn, Johns Hopkins Studies,^ 

 Vol. Ill, No. 1.) points out that the antenna is lacking entirely, and 

 is not rudimentary as Birge has drawn it. 



Pinnotheres maeulatus Say. " Mussel Crab." 



Plate II. Figure 7. 

 Pinnotheres maculatum Say. 



This crab is slightly smaller than P. ostreum, about the same 

 shape, but has a thicker and firmer carapace. The males are very 

 small; in color they are nearly black, with spots of white. 



Habitat: female in the gill chamber of the common mussel and 

 scallop; male, free-swimming at the surface. 



