12 



BULLETIN 97, UNITED STATES NATIONAL MUSEUM. 



idae (not included in this volume), in which the young issues from 

 the egg as a tiny crab substantially like its parent. 



Surprisingly little is loiown of the development of different species, 

 as the life history of not more than a dozen of our American species 

 of Brachyura has been worked out. This would prove a fruitful 

 field for investigators in our seaside laboratories where facilities 

 are offered for studying transformations in the aquarium. 



It is unwise to draw sweeping conclusions from a few cases, for 

 recently the discovery has been made of the direct development of the 

 young crab from the egg in a species of the Oxyrhyncha or spider- 

 crabs.^ 



ANALOGOUS SPECIES ON OPPOSITE SIDES OF THE CONTINENT. 



Throughout this volume, after the keys to species, I have indi- 

 cated in parallel columns those closely related species occurring on 

 opposite sides of the continent. The resemblance between the units 

 of some of these pairs is much greater than between others. All 

 are here assembled in a single list, followed by a list of those species 

 which occur on both sides of the continent ; those of world-wide range 

 being indicated by an asterisk (*). 



Family GONEPLACIDAE. 



Atlantic. 

 Prionoplax atlantica. 

 Eiiryplax nitida. 

 Spcocarcinus carolinensis. 

 Glyjttoplax smithii. 

 Chasmocarcinus typicus. 



Pacific. 

 Prionoplax cUiata. 

 Euryplax poUta. 

 Spcocarcinus granuUmanus. 

 Glyptoplax pugnax. 

 Chasmocarcinus latipes. 



Family PINNOTHERIDAE. 



Pinnotheres ostreum. 



Fahia byssoniiae. 

 Parapinnixa hcndcrsoni. 

 Parapinnixa hotivieri. 

 Pinnixa hrevipollex. 

 Pinnixa faxoni. 

 Pinnixa cyVmdrica. 

 Pinnixa sayana. 

 Pinnixa floridana. 



Pinnotheres holmesi. 

 Fahia canficJdi. 

 Parapinnixa nitida. 

 Parapinnixa affinis. 

 Pinnixa afflnis. 

 Pinn ixa transversalis. 

 Pinnixa franciscana. 

 Pinnixa occidentalis. 

 Pinnixa longipes. 



Family CYMOPOLIIDAE. 



Cymopolia altemata. 

 CymopoUa faxoni. 

 Cymopolia ohesa. 



Cymopolia zonata. 

 Cymopolia lucasii. 

 Cymopolia tuherculata. 



» See stalk-eyed Crustaceans collected at the Monte Bello Islands. By Mary J. Rath- 

 bun. Proc. Zool. Soc. London, 1914, pp. G53 and GG2. 



