Vol. XXII, pp. 107-114 June 25, 1909 



PROCEEDINGS 



OF THE 



BIOLOGICAL SOCIETY OF WASHINGTON 



NEW CRABS FROM THE GULF OF SIAM.* 

 BY MARY J. RATHBUN. 



The forms here described are part of a collection made by 

 Dr. Theodor Mortensen in the Gulf of Siam in 1899-1900. A 

 full report with illustrations will be published in Det Kongelige 

 Danske Videnskabernes Selskabs Skrifter. The type specimens 

 are in the Museum at Copenhagen. 



Family LEUCOSIID^. 



Subfamily LEUCOSIIN.E. 



Heteronucia tnesanensis sp. nov. 



Type. — 9 ) between Koh Mesan and Koh Chuen, 15 fathoms. 



Dimensions. — Length, 3.7 mm. ; width, 4.5 mm. 



Carapace covered with veniculous granules, suliglobular, very uneven ; 

 cardiac and mesogastric regions set off by a deep groove ; branchial region 

 nodulous. On the pterygostomian region a large obtuse-angled promi- 

 nence in line with the eye. Front and orhits nearly one-half as wide as 

 carapace; front with a median furrow and faintly bidentate. Outer 

 maxilliped bent almost at a right angle near its middle. Chelipeds 

 knobby, palm very thick proximally, as long as fingers which are 

 evenly denticulate and overlap, dactylus lying within pollex. 



Cryptocnemus mortenseni sp. nov. 



Type. — c?, Koh Chuen, 30 fathoms, shell bottom. 



Dimensions. — Length, 3 mm. ; width, 3.8 mm. 



Near C. pentagonus Stimpson. Margin of posterior half of carapace 

 regularly arched ; of anterior half slightly angled at hepatic region ; edge 

 of front arcuate. Carapace surrounded by a thin striated rim, widest at 

 postero-lateral region, and continued downward to anterior margin of 

 buccal cavity, forming lower margin of a facet, of which upper edge is 

 blunt. Chelipeds with striated marginal crests; palm IJ4 times as long 

 as wide; immovable finger broadly triangular, sharp-pointed; dactylus 

 strongly bent down. 



* Published with the permission of Dr. Theodor Mortensen. 



16— Proc. Biol. Soc. Wash., Vol. XXII, 1909. (107) 



