2^2 SMITHSONIAN MISCELLANEOUS COLLECTIONS 



Genus tETHRA Leach 



The large basal joint (basiocerite) of the external antennae in this, 

 genus is not soldered to the adjacent parts, but is movable as in 

 Ceratocarcinus. This adds another character to those mentioned by 

 De Haan as approximating it to the Parthenopidse. The two genera 

 are also similar in their short and broad epistome, and the ridges of 

 the palate. Future researches may indicate that they, with one or 

 two other genera, form a group distinct from both PaythenopidcE- 

 and CancridcB. 



38. ^THRA SCRUPOSA (Linnaeus) Milne Edwards 



Cancer scruposus Linn^us. 



^thra depressa Lamarck, An. sans vert., v, 265. 



Mthra scruposa Milne Edwards, Hist. Nat. des Crust., i, 371 ; Cuv. R. A.,. 



pi. XXXVIII, fig. 2. GuERiN, Icon., pi. XII, fig. 3. Dd Haan, loc. cit.,. 



p. 81. 



Taken among the islands of Caspar Straits by Mr. L. M. Squires,, 

 of the "John Hancock." 



Genus CERATOCARCINUS Adams and White 



Dana was the first to give the essential characters of this genus,, 

 and to point out the remarkable fact that the basal joint of the an- 

 tennas is not soldered to the adjacent parts, as in other genera of 

 Parthenopidse, and, in fact, almost all Brachyura. This observation 

 we are enabled to confirm from examination of full-grown speci- 

 mens. The joint is flattened, and, fitting closely in the cavity which 

 receives it, does not interrupt the general surface ; so that it is only 

 by the application of force that its mobility is discovered. The- 

 "coxocerite" containing the organ of hearing is very small and placed, 

 close below the basal joint. The eyes are retractile. 



Harrovia of Adams and White agrees in all essential characters 

 with Ceratocarcinus. In the orbits, antennse, gnathopoda, and in 

 general appearance they are nearly the same. In their diagnosis of 

 Harrovia the authors do not even mention the characters which are 

 of most importance in a generic point of view, their description 

 being confined to details of shape, granulation of surface, dentition 

 of margin, etc. Why they should place the crab among the Leuco- 

 sidce it would be difficult to decide. 



