106 



Contributions to Palceontology . 



resembling the flabelliform muscular impressions of the 

 ventral valves of Okthis, like 0. oblata and 0. vanuxemi. 

 The muscular impression in the spatulate valve is narrow 

 above, gradually widening in the middle, with a central 

 line : while its lower part is divided into three lobes, the 

 central one shorter, the lateral ones longer, and diverging 

 so that the outer margins of the impression are nearly 

 parallel to the margin of the shell. The central longitu- 

 dinal line seems to have been made by an extremely thin 

 septum, which does not reach to the lower extremity of 

 the central muscular impression. 



Although several specimens of the broader and shorter 

 form have been exfoliated so as to show the muscular 

 impression, they are all of the same character, and I am 

 compelled to infer that they are of the same valve. At the 

 same time, three individuals of the spatulate form (which 

 have been exfoliated with much difficulty) all presented an 

 identical form of muscular impression. 



Notwithstanding that these fossils have all the external 

 characteristics of Lixgtjla, from which it would be very 

 undesirable to separate them, were it possible to do other- 

 wise, yet the form of muscular impressions is so unlike 

 that of modern Lixgula, as well as those in the Devonian 

 rocks which I have seen, that it becomes necessary to pro- 

 pose some other designation. In order to retain some 

 indication of their relations, I propose the name Lixgu- 



GENUS LESTGULEPIS (n.g.). 



Shells linguloid, inequivalve, equilateral, oval-ovate or 

 spatulate : muscular impression, in one valve, flabelli- 

 form ; in the other, tripartite, the lateral divisions larger. 

 Shell corneous, phosphatic. 



The characters above described are from specimens of apparently 



