Dall — Miocene and Pliocene of Martha 's Vineyard. 299 



excavated behind the beaks, subtruncate obliquely, below ; two 

 obscure impressed lines radiate from the beak to the lower 

 posterior margin ; the valves appear to have been otherwise 

 smooth ; muscular impressions large, distinct ; pallial sinus in 

 the right valve rising before the adductor scar then suddenly 

 sloping and rounded off but little in front of the beak ; in the 

 left valve the sinus is more evenly arched above and extends 

 much further forward, nearly reaching the anterior adductor. 

 Lon. of cast 45 ; alt. 40 ; diam. lY mm . 



This species is closely related to Macoma obliqua J. Sby. 

 (sp.) of the English Crag, but is less produced in front and 

 more excavated on the posterior dorsal margin. It is also more 

 sharply flexed behind. This is the shell mentioned by Sir 

 Chas. Lyell as " a Tellina resembling T. biplicata" 



It will be observed that this is a distinctly northern assem- 

 blage ; any of the species might be at home in the waters about 

 Gay Head to-day, as far as we can judge by analogy in the case 

 of extinct species. 



As regards correlation with the divisions of the Southern 

 Miocene it may be said 1 : that the Gay Head Miocene is Chesa- 

 peake and not older; and 2, that it belongs in all probability 

 to the upper part of the Chesapeake, certainly not lower than 

 the St. Mary's fauna, and probably between that and the York- 

 town beds. 



About eighty feet above sea-level, in a layer of sand uncon- 

 formably overlying the Miocene beds and involved in the Gay 

 Head uplift, a small patch of shell fragments was discovered 

 and carefully collected by Mr. J. B. Wooclworth. The frag- 

 ments were well preserved and not badly worn though broken, 

 and the species identified were as follows : 



Venericardia borecdis Conrad. 

 Astarte castanea Say. 

 Spisida. poly Hymn Stm. 

 Corbicula densata Conr. 

 Macoma Lyellii Dall? 

 Nxicula Shaleri Dall, var. ? 

 Purpura lupillus L. 



The fragment of Macoma fits exactly upon the beak of one 

 of the internal casts of M. Lyellii from the Miocene. The 

 single valve of JVucida is larger than the Miocene specimens, 

 has a slightly more rounded base and a few more teeth on each 

 side of the hinge ; but these are characters which denote greater 

 maturity and there can be but little doubt that the shell is the 

 same. Corbicula densata was described from the upper Mio- 

 cene of Virginia and occurs in the Pliocene of South Carolina, 

 and the Venericardia is of the recent type rather than the Mio- 



