Maryland Geological Survey 355 



Rhynchonella campbellana Hall, 1859, Nat. Hist. N. Y., Pal., vol. ill, p. 239, 



pi. xlili, fig. 2. 

 Uncinulus campbellanus Schuchert, 1897, Bull. U. S. Geol. Surv., No. 87, p. 



458. 



Description. — " Shell longitudinally oval, ovate or oblong, laterally 

 compressed, two-thirds as broad as long, length and height about equal : 

 dorsal valve the larger, elevated near the front into a broad undefined 

 mesial fold, declining neai' the beak and curving down abrui)tly at the 

 sides ; beak incurved : ventral valve compressed, abruptly deflected towards 

 the opposite valve at the lateral margins, depressed into a broad rounded 

 sinus which occupies almost the entire breadth of the narrow front; 

 front margin curving upward, and extended into a triangular prolonga- 

 tion. Surface marked by twenty-two or twenty-four simple rounded sub- 

 angular plications, five or six of which are elevated on the mesial fold, and 

 four or five occupy the sinus of the ventral valve. Fine zigzag lines of 

 growth are seen on the front of the shell, near the junction of the valves." 

 Hall, 1857. 



Length 2.5 cm. ; width 2.3 cm. 



Specimens of this easily recognized rhynchonelloid were collected by 

 Rowe at Warren Point, and agree very well with those from New York. 

 The dorsal apex of one of the southern specimens was ground down and 

 showed the large and strong solid median septum so characteristic of 

 Plethorhyncha. This is, therefore, the earliest or oldest species of this sub- 

 genus and it leads directly into C. jwcvspeciosa, which is as large again 

 and has from ten to twelve more plications on each valve than C. caiiip- 

 h ell ana. 



Occurrence. — HelderberCx Formation, ISTew Scotland Member. 

 Warren Point, Pennsylvania. 



Collection. — Maryland Geological Survey. 



Camarotcechia (Plethorhyncha) pr^^speciosa n. sp. 



Plate LXIII, Figs. 20, 21 



Descrijition.. — In the ]\laryland collections, this shell has heretofore 



been confounded with Uiiciiiulu.'< nobilis (Hall). H differs, however, in 



being more elongated, has more abrupt flattened sides, the ventral sinus 



