316 



REPORT ON THE STATE CABINET. 



" GENUS EICHWALDIA, Billings. 



" Generic Characteks. — Large valve perforated ou the umbo for the passage 

 of the peduncle ; the place of the foramen beneath the beak occupied by 

 an imperforate concave plate, the interior divided by an obscure medio- 

 longitudinal ridge ; interior of smaller valve divided throughout from the 

 beak to the front by a very prominent medio-longitudinal ridge ; no hinge- 

 teeth, sockets, or other articulating apparatus in either valve. 



"After a gi'eat deal of examination and comparison, I have not been able to 

 refer the species for which the above generic name is proposed to any of the 

 described genera. Although several silicified specimens exhibiting the interior 

 have been obtained, they do not show any muscular impressions. The perfo- 

 ration on the back of the beak was at tirst supposed to be a fracture, but we 

 have now specimens which exhibit its characters so completely that I do not 

 think it possible there can be any mistake. The internal structure of the larger 

 valve somewhat resembles that of Pentajvierus or Camarophoria, the concave 

 plate beneath the beak appearing to be the homologue of the floor of the 

 triangular chamber fcmnd in these genera. I cannot make out, however, that it is 

 in any way connected with the medio-longitudinal ridge, as is the case in both 

 Pentamerus and Camarophoria. In removing the limestone from silicified 

 specimens, the delicate processes in the interior of species of Brachiopoda are 

 very often destroyed ; and it is possible that the connection in question may 

 exist in perfect specimens, but not appear after treatment with acids. It is, 

 therefore, uncertain whether or not it is attached to the plate beneath the 

 beak. If it should be hereafter ascertained that it is so connected, the foramen 

 on the umbo would still be sufficient to show that this is a new genus, to the 

 establishment of which the characters of the smaller valve and the absence of 

 any articulating and apophysary apparatus would be additional characters." 



Although not entirely corresponding with some parts of the above 

 description, I conceive that the species I have referred to this genus 

 really illustrate its true charac- ^ „ 



•^ Fig. 2. 



ters. The accompanying fig. 1 ^...^r-nn^ 



illustrates tlie general form and ..df^-''^!'Mk:j:-.-?^.. 

 surface texture of Eichwaldia reti- 

 culata of the Niagara group, from 

 Waldron, Indiana. Fig. 2 is a cardinal view of the 

 same, showing a smooth or denuded beak. 



An enlargement of the surface shows a texture like the accompany- 

 ing figure 3, which is carefully drawn from the specimen figured. A 

 vertical section of the shell enlarged, fig. 

 4, shows the superficial textile spaces 

 narrowing downwards, and the inner 

 layer of the shell become solid. The exterior reticulate 

 structure of the shell is therefore a part of the shell proper. 



Fir ^ 



Fig. 4. 



