LAMKLUHKAV IIIATA. 621 



Type: Cunfitmya iiiiamifiisis Hall ami Whit field. 



This -.'nil- i- represented in my cabinet by no less than sixteen, mostly unde- 

 M ril>ed, Ix)wer Silurian specific forms, all of which, saving the two about to be 

 described, were found above the top of the Trenton at Cincinnati and other localities 

 wit hin a radius of forty miles from that city. Several of these species are represented 

 by casts of the interior in as fine a state of preservation as could be desired, and yet 

 in no case was it possible to reach any satisfactory conclusion respecting the 

 character of the muscular and pallial impressions. Under the circumstances it is 

 not unlikely that the claim of the authors of the genus that the pallial line is simple, 

 m iY te nothing more than the expression of their opinion and not the record of an 

 observed fact In their description of the genus Hall and Whitfield state also that 

 posterior to the external ligament "the margins of the valves overlap each other to 

 the extent of the cardinal line." This may be true of the specimens studied by them 

 but, except in several cases where it is evidently the result of accident or compres- 

 sion, it is certainly not true of any specimen seen by me that is sufficiently perfect 

 to admit of judgment on the point. The statement, therefore, wants confirmation 

 before it can be accepted as a fact. So far as my own observation is concerned, I 

 am obliged to dissent from such a view, especially as regards C. miamiensis the type 

 of the genus, of which several specimens that seem to have retained the valves in a 

 perfectly normal relation, have the escutcheon divided equally by the straight con- 

 tact margins of the valves. 



As regards the external ligament, it is preserved by only two specimens seen by 

 me. One of these belongs to C. curia Whitfield, the other to C. coriformis Miller. It 

 is elongate (almost linear), occupies about one-third of the width of the escutcheon 

 ami extends from the beaks backward a little more than one-third of the length of 

 the escutcheon. The same specimens preserve also something like a ligament over 

 the margins of the valves in the lunule. 



The affinities of the genus are almost certainly with (irammyxin as that genus is 

 defined by Hall in his great work on Devonian Lamellibranchiata (Pal. N. Y., vol. v, 

 pt i, pp. xxx and 358-384.) The principal difference between the genera as now 

 recogni/ed lies in the hinge, this being weak and edentulous in Cutuamya while it is 

 stronger and presents one or two cardinal folds in at any rate the typical forms of 

 i -.i in in ;/-i'i. Shells probably belonging to this genus have been referred to Sedg- 

 uirki'i and Leplodomus, but as it seems, upon very insufficient grounds, the types of 

 those genera, as defined by McCoy in 1844, (Synopsis Carb. Foss. Ireland) being of a 

 widely different nature. The new genus i <litinpii>hel by its peculiar 



hinge, much smaller beaks, and strongly defined anterior muscular scar. 



