Vol. 70.] THKOUGH THE AXDES OF PERU AND BOLIVIA. 35 



It appears doubtful whether D'Orbigny's type of JPr. boliviensis 

 must rank as a separate species from the above, and little can 

 be gleaned from his idealized drawings l ; but, if we turn to 

 ■Chernyshev's interpretation of the species as represented in the 

 Urals, we can trace a close resemblance with the Bolivian shells. 

 This author states that he has seen D'Orbigny's type -specimen, 

 and, as he still retains the specific name for his Uralian examples, 

 the} 7 " evidently differ somewhat from our common British semi- 

 reticulate forms. 



The incipient smoothness of the margin of the shell and the 

 nodular character of the semireticulation are also, apparently, 

 features of A. d'Orbigny's species, as is shown by Chernyshev's 

 figures. 2 



EXTELETES af£. HEMIPLICATA Hall. (PL VIII, figs. 2 a-2 c.) 



This genus, of which the type is Enteletes lamarchi of Fischer 

 •de Waldheim from the Moscovian of Russia, was reintroduced 

 by Waagen, in order to supersede the name Syntrielasma of 

 Meek & Worthen. 



As representative of a subfamily of the Orthidse, it includes 

 • certain resupinate forms, which show advanced characters suggestive 

 of a passage from the Schizophorids to the Rhynchonellids. The 

 genus has been fully described by Waagen, 3 and it is only necessary 

 here to restate a few of its more important features : such as, 

 the strong plication of the valves ; the presence of a thin blade-like 

 median septum between the dental plates in the pedicle-valve ; and 

 the extreme development of the brachial ' crura.' . The same author 

 lias subdivided the genus into two groups : ' Ventrisinuati ' and 

 ' Dorsosinuati \ — according to the presence of the median sinus on 

 the ventral or on the dorsal valve. Such a division, however, 

 does not appear to be absolute, as in many examples there occurs 

 incipient plication of the actual fold and sinus — thus reversing 

 the conditions, and suggesting a transition from one group to the 

 other. 



The occurrence of this genus in the Carboniferous Limestone of 

 Bolivia, represented by a single well-preserved specimen brought 

 back by Col. Lloyd from Arque in the Oruro district, is a point of 

 some interest, for the genus is characteristic of the Middle and 

 Upper Coal Measures in the United States, and survives in the 

 Lower Gruadalupian fauna of New Mexico and the Permian of the 

 Salt Range. Waagen' s species from the Salt Range are almost all 

 dorsosinuate forms, 4 and differ in their more pronounced folding 

 from the Bolivian specimen, which bears very close resemblance 

 to Enteletes liemiplicata of Hall from the Upper Coal Measures 



1 ' Voyage dans l'Amerique Meridionale : Palaontologie ' 1842, pi. iv, figs. 7-9. 



2 Mem. Com. Geol. Eussie, vol. xvi, No. 2 (1902) pi. xxxii, fig. 5 & pi. xxxv, 

 fig. 3. 



3 Pal. Indica, ser. 13, vol. i (1887) p. 550. 



4 Ibid. pi. lvii, figs. 1-8. 



d2 



