No. 109.] 123 



Meganteris subtrigonalis (n. s.). 



Pal. N.Y. Vol. iv. 



Shell subtriangular, broadest above the middle, rounded at the 

 lateral extremities, sloping towards the front, -which is some-vvhat 

 narrowly rounded : dorsal valve the smaller, depressed-convex, 

 most elevated a little above the middle; front slightly depressed ; 

 beak incurved : ventral valve most elevated along the middle, 

 gibbous a little above the centre, sloping laterally and towards 

 the front, where it is sometimes depressed. Surface smooth, or 

 marked by faint lines of growth. 



Geological posilion and locality. Limestone of the Upper Ilelderberg 

 group, Erie county ( N.Y.). 



Meganteris elongatus. 



Pal. N.Y. Vol.iv. 



Pentamerus elongatus, Yanuxem : Rep, 3d Geol. Dist. N.Y. p. 132. 



This species, which has usually been referred to the Genus Peritamerus, 

 is a true Meganteris. Fragments of it are not unfrequent in the Onondaga 

 limestone, but perfect specimens are rarely met with. It has much the form 

 of the elongated varieties of M. oroides of the Oriskany sandstone, but 

 appears to have been nearly destitute of radiating strias, or preserving only 

 faint traces of them, although the concentric wrinkles of growth are some- 

 times quite distinct. It resembles yet more closely Terehratula caiqua 

 ( See DUNKER und Yon Meyer, Paliiont. u.s.w. dritter land, 4, tab. 26, 

 f . 5 ) ; but in.stead of a round perforation in the beak of the ventral valve, 

 it appears to have been provided with a triangular foramen. This character, 

 however, may depend on the state of preservation or perfection of the 

 specimen. 



Geological posit inn mid localitij. Ononrlnfa limestone of the Upper 

 Helderberg group, Onondaga and Ontario counties. 



