708 CA MBEIAN BHACHIOPODA— walcott. 



species of Jphidea {I. superha) from the Middle Cambrian Tonto sand- 

 stone (»f the (irand Canyon of the Colorado. In this form the ventral 

 valve is bioadly conical, and the larjie j)scudodeltidium projects back- 

 ward at an angle equal to that of the slope from the ai)ex to the front. In 

 I. bdla tlio false area slo])es more abruptly downward, and in f. onudelhi 

 it is nearly vertical, the pseudodeltidium being much shorter and pro- 

 jecting but a short distance beyond the area. The slope of the area 

 of /. ornaieUa is essentially the same as that of /. lahradoriat var. 

 su-antonensifi, which is the type of Mr. Ueecher's genus Futerina. In 

 some specimens of the latter species the beak projects so that the slope 

 of the area carried it forward to a considerable distance under the beak. 

 This is also true of I. pannula. 



The presence of an apical foramen in I. bella and /. ornatelln would 

 separate the genus from Paterina, but, from a careful study of all the 

 evidence attainable, I am led to question the presence of a true apical 

 foramen in either species. Unless there are other characters than tliose 

 shown by the false area and i)seudodeltidium and the angle at which 

 they slope, it will be imi^racticable to generically separate I. bella and 

 I. J((br<tf1oricus and the other species mentioned. 



In his original description, Mr. Billings says: 



In the specinieu above figured there is au aperture iu the beak, but in another 

 there is no appearance whatever of a perforation.' 



Professor Whiteaves writes me, under date of July 23, 189G, that 

 there are no si)ecimens or electrotypes of the types of I. bella in the 

 collections of the Geological Survey of Canada, nor of the closely 

 allied species of the same genus from Topsail Head, mentioned by 

 Mr. Billings. Under the circumstances, nothing can be done but to 

 decide from Mr. Billings's description and figure the characters of the 

 genus and species, and refer to the species the form that can best be 

 identified with the description and figure as the specific type of the 

 genus. This appears to be the species from the York limestone of 

 Pennsylvania. 



In a fine series of Iphidea bella from tlie Lower Cambrian, south of 

 Emigsville, York County, Pennsjdvania, the characteristics of tlie genus 

 and species are strikingly well shown. In none of the specimens is there 

 in the ventral valve an indication of an apical pedicle opening. The 

 dorsal valve is slightly elevated, and in the half dozen well-preserved 

 specimens no trace has been observed of any false area or pseudo- 

 deltidium; but in 7. pajmula the false area is even more clearly defined 

 than in the ventral valve, and the pseudodeltidium is ])resent as a 

 depressed concave covering of more than one half of the triangular 

 space inside the narrow area on ea(;h side. The area on the dorsal 

 valve has also been observed in I, oruatella and /. labradorka. 



Doctor liinnarsson, in describing /. ornatcUa, speaks of the presence 

 of a minute foramen ; but, after the study of several finely preserved 



' Pal. Foss., II, Pt. 1, p. 76. 



