GENUS EICHWALDIA. 



275 



exhibit its characters so completely thai I do not think it possible there can be any 

 mistake. The internal structure of the larger valve somewhat resembles that of 

 Pentamerus or Camarophoria, the concave plate beneath the beak appearing to be 

 the homologue of the lioorof the triangular chamber found in these genera. I cannot 

 make out, however, that it is in any way connected with the raedio-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 Bra- 

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

 may exist in perfect specimens, but not appear afcer 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 characters. The accompanying fig. 1, illustrates the 

 general form and surface texture of E. reticulata of the Niagara group, 

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

 smooth or denuded beak. 



Fig. 1. Fig. 2. 



EiCHWALDiA RETICULATA : dorsal vicw. E. RETICULATA : Cardinal view. 



An enlargement of the surface shows a texture like the accompanying 

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

 section of the shell, fig. 4, shows the superficial textile spaces 'narrowing 

 downwards, and the inner layer of the shell becomes solid. The exterior 

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

 Fig. 3. Fig. 4. 



E. RETICULATA : 



enlargement of the surface. 



E. RETICULATA : 



a vertical section of the shell enlarged. 



The interior of the dorsal valve, fig. 5, shows a narrow longitudinal 

 septum, s, which, beginning at the apex, reaches nearly to the base of the 

 shell. The great elevation of this septum is shown in figure 7. There is a 



