PALEONTOLOGICAL NOTES, NO. V. 



A NEW FOSSIL CRAB FROM THE MIOCENE GREENSAND 

 BED OF GAY HEAD, MARTHA'S VINEYARD, WITH 

 REMARKS ON THE PHYLOGENY OF THE GENUS 

 CANCER. 



By Alpheus S. Packard. 



Received May 3, 1900. Presented May 9, 1900. 



In looking over a small collection of fossil crabs made by Mr. J. H. 

 Clarke of Providence, R. I., about thirty years ago, there occurred one 

 specimen which represented quite a different group from Stimpson's 

 Archaeoplax signifera. It came, he told me, from the same bed and 

 locality at Gay Head as the other crabs. 



On consulting with Mr. Walter Faxon, assistant in charge of the 

 Crustacea of the- Museum of Comparative Zoology, who kindly showed 

 me the fossil crabs of the collection, we concluded that though the 

 body was very round and the surface of the carapace much more 

 convex, it could not belong to any other genus. Mr. J. B. Wood- 

 worth also kindly allowed me to examine a trayful of fragments of 

 Archaeoplax collected by him while connected with the U. S. Geologi- 

 cal Survey, from the greensand bed at Gay Head. Among them was 

 the hand of what was plainly enough that of a large Cancer, like our 

 common C. irroratus, and it seemed evident that it must have belonged 

 to a large individual of the same species as the small crab. Both still 

 retained more or less of the greensand, and the hand was loosely em- 

 bedded in a matrix of that material. For the opportunity of describing 

 the hand, I am indebted to the U. S. Geological Survey. 



Cancer proavitus, n. sp., Plate I., Figs. 1,2, 3. One young male repre- 

 sented by the carapace, sternum, and basal joints of the legs. All the 

 teeth on the front edge of the carapace absent except the two on the left 

 side of the left orbit. 



Body much narrower, and therefore rounder, more orbicular than in 

 the existing species. 



