No. 109.] 123 



Meganteeis subteigonalis ( n. s.). 



Pal. N.Y. Vol. iv. 



Shell subtriangular, broadest above the middle, rounded at the 

 lateral extremities, sloping towards the front, which is somewhat 

 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 position and locality. Limestone of the Upper Helderberg 

 group, Erie county ( N.Y.). 



Meganteeis elongatus. 



Pal. N.Y. Vol. IT. 



Pentamerus elongatus, Vanuxem : Eep, 3d Geol. Dist. N.T. p. 132. 



This species, whicli has usually been referred to the Genus Pentamerus, 

 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. ovoides of the Oriskany sandstone, but 

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

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

 times quite distinct. It resembles yet more closely Terebratula caigua 

 ( See DuNKER und Von Meter, Palaont. u.s.w. dritter band, 4, tab. 26, 

 f . 6 ) ; but instead 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 position and locality. Onondaga limestone of the Upper 

 Helderberg group, Onondaga and Ontario counties. 



