TIic Fossil Crab of Gay Head. 583 



in some characters, while they are widely difFerent in others. 

 Thus the external niaxillipeds, the chelipeds, the pt(!rygo- 

 stomian region, the posterior tooth of the antero-lateral 

 border, in all except inniidus, are very much alike. The 

 shape of the abdomen in both the male and female, is 

 quite characteristic of the species, in this genus. 



The materials upon which the above observations were 

 made are in the Museum of Comparative Zoology at 

 Cambridge and that of the Smithsonian Institution at 

 Washington. 



Art. XIV. — On the Fossil Crab of Gay Head. — By 

 Dr. William Stimpson. 



[Communicated January 21, 1S63.J 



The occurrence of remains of Crustacea in the gi-een- 

 sand layer of the interesting series of strata exposed at 

 Gay Head, the southwestern extremity of Martha's Vine- 

 yard, has long been known. Dr. Hitchcock alludes to 

 them in the first edition of his " Geology of Massachu- 

 setts," published in 1833, as well as in the second edition 

 of the same work (1841). They are there described in 

 the following terms, which we give entire, as showing the 

 lithological character of the specimens : — 



" Crustacea. In the green sand at Gay Head, we meet 

 with well-characterized specimens of the genus Cancer, 

 although they are in general much broken ; showing that 

 they originally belonged to a formation which was abraded 

 or destroyed anterior to the production of the green sand. 

 The interior part of the specimen consisted of argillaceous 

 matter, probably containing a large proportion of oxide of 

 iron ; but the covering of the animal still retains its black 

 shining color, although apparently carbonaceous. The 

 broken state of nearly all the specimens, renders it difficult 

 to determine whether they belonged to more than one spe- 



Ai'KiL, 1863. 



