LOWER SILURIAN LAMELLIBRANCHS. 685 



Genus TECHNOPHORUS, Miller. 

 Technophorus picnctosiriattcs, n. sp. 



Plate 4? Figs. 10-12. 



Shell small, moderately convex, alated posteriorly, the height and 

 length nearly as two is to three. Cardinal margin long, nearly straight, 

 in front passing rather regular^ into the rounded auterior margin, behind 

 drawn out into a small, compressed, triangular wing, the acuminate ex- 

 tremity of which projects slightly beyond the post-basal angle; ventral 

 margin nearly parallel with the dorsal, straight in the middle and behind, 

 curving regularly upward anteriorly; posterior margin biconcave, the 

 upper concavity less oblique and twice as long as the lower. Beaks small, 

 projecting very little in both the shell and in casts of the interior, situ- 

 ated, in specimens of the usual size, only about one tenth of the entire 

 length of the shell in front of the middle. Two strong and sharp ridges 

 extend in a strongly curved direction from the beak across the posterior 

 half of the valves to the lower part of the posterior margin. With the 

 exception of the posterior wing, the surface is marked with regular 

 raised concentric lines, separating series of small punctae. The latter 

 may be arranged in quincunx or in lines radiating from the beaks. Three 

 or four of the concentric lines occur in the space of 1 mm. The poste- 

 rior wing is marked by similar lines but here they are straight and oblique, 

 following a direction at right angles to a line drawn from the post-cardi- 

 nal angle to the antero-basal margin. Of internal characters we know 

 only that the clavicle was short and blunt, yet very strong, and that the 

 cavity immediately in front of it contains a small and faintly denned 

 muscular impression. 



This small species is decidedly like the T. subacutus, Ulrich, from 

 the lower Trenton of Minnesota, vet I have no doubt that they are spe- 

 cifically distinct. At present we know that .species only from a cast 

 of the interior. Comparing this with casts of the present shell we find 

 that in the earlier form the beaks are more prominent and situated far- 

 ther forward, the cardinal outline is different and the posterior ridges 

 much less distinct. In the associated T. faberi, Miller, the posterior 

 wing is shorter and the surface markings consist, so far as known, of very 

 fine concentric lines only. It is besides a larger shell. 



Formation and Locality : Middle beds of the Cincinnati group, Cov- 

 ington, Kentucky, where it occurs at an altitude of from 300 to 350 feet 

 above the bed "of the Ohio River. 



Technophorus yoldiiformis, Ulrich. 



Plate 47. Figs. 13 and 14. 



Nuculites yoldiaformis, Ulrich, 1879, Jour. Cin. Soc. Nat. Hist., vol. ii, p. 24. 



Though not entirely satisfied with the present generic arrangement 

 of this peculiar species, I am still convinced that it is nearer the truth 



