344 J/. J. Rathbun — Fossil Crab from Port Townsend. 



Art. XXIY. — Description of a New Genus and Species of 

 Fossil Crab from Port Townsend, Washington ; by Mary 

 J. Rathbun, Associate in Zoology, United States National 

 Museum. 



The crab described in this paper was presented to the Yale 

 Museum in 1873 by Dr. Thomas T. Minor, a graduate of the 

 University. Although it is from the late Tertiary, the exact 

 horizon is not known, and according to Dr. John C. Merriam, 

 of the University of California, who has kindly examined the 

 specimen, it is impossible even with a fair knowledge of the 

 geology of the region to state its position with certainty. 



For the privilege of making the description I am indebted 

 to Prof. Charle6 Schuchert. 



Tribe BRACII1URA. 

 Subtribe Bracliygiiatlia. 

 Superfamily BRACHYRHYNCHA. 

 Family Goneplacidae. 



Branchioplax, gen. no v. 



Carapace a little broader than long. Anterior margin arcu- 

 ate. Orbits of moderate size. Antero-lateral margins dentate 

 and very short, about half as long as postero-lateral margins, 

 which are subparallel, but with the posterior angles rounded. 

 Front not emarginate. Regions well defined, branchial regions 

 swollen dorsally and approximate. Chelipeds unequal, of 

 moderate length, carpus not much broader than long, manus 

 high. 



(ftpd<y%ia, gills, branchiae, in allusion to the swollen bran- 

 chial region ; 7rXa|, anything flat and broad, carapace.) 



This genus is akin to the recent genus Eucrate de Haan* 

 (type, E. crenata de Haan, from Japan), of the subfamily 

 Carcinoplacinae, but differs in having an entire front, that is, 

 uninterrupted by a median emargination or by a separate small 

 tooth at the inner angle of the orbit ; in the narrower and 

 more oblique orbit ; in the shorter antero-lateral margin with 

 only two teeth, and those distant from the orbit ; in the after 

 part of the carapace being squarer, the sides subparallel in part 

 instead of constantly converging ; in the more areolated cara- 

 pace and less massive and very unequal chelipeds. 



Type of the genus, JB ranchioplax toashingtoniana. 



As the characters of the ventral surface are not known, it is 

 impossible to assign the genus to its subfamily. 



* Fauna Japon., Crust., p. 36, 1835. 



