584 The Fossil Crab of Gay Head. 



cies, although they probably did ; and for the same reason 

 I have thought that drawings would not be of use." 



In the summer of 1859 a large number of specimens of 

 these fossil crabs were collected by Mr. Ordway * and my- 

 self, and in 1862 collections were made at the locality by 

 Messrs. Hyatt and Shaler, which include some of the best 

 examples yet found. These materials, though abundant, 

 consist for the most part of small fragments ; and there are 

 none which are sufficiently well-preserved to give a proper 

 idea of the entire crab. By the btudy and comparison of 

 these fragments, however, I have been able to refer them 

 all to two species, both brachyuran. Only one of them is 

 sufficiently well represented by specimens to enable me 

 to judge of its perfect form and true place in the system. 

 To this species nine tenths of the fragments belong, and 

 by the combination of these, I have endeavored to repro- 

 duce the essential parts of the crab, and to represent them 

 in the accompanying diagrams. 



I cannot refer the species to any described genus, either 

 recent or fossil ; but there is abundant evidence that it be- 

 longs to the Carcinoplacidae of Mihie-Edwards,! of which 

 family it forms a new genus and species. It may be called 



ARCIIAKOl'LAX SIGNIFKRA. 

 IM. XII., figs. 1-4. 



The carapax is remarkable for its great posterior breadth. 

 This is, indeed, characteristic of the family Carcinoplacidae^ 

 which are consequently placed in the great group Ocijpod- 

 oidea, notwithstanding that the conformation of their 

 maxillipeds and sternum resembles closely that found in 

 Cancroids. The approximate length of the carapax (PI. 

 XII., fig. 1.) in the best specimen is 1.6 of an inch ; its 

 greatest breadth is 2 in., and the breadth at the posterior 



* The instructive specimens in the Museum of Comparative Zoology, developed 

 by this gciitleinnii, hsive aitlcd me much, 

 t Melanges Carcinologi(iucs, p. 128. 



