32 ME. J. A. DOUGLAS OX GEOLOGICAL SECTIONS [April 1914, 



Palseontological Notes. 



Sl'Irifee condor D'Orb. (PI. IX, figs. 1#-1 c.) 



This species, first figured and described by A. d'Orbigny from 

 Yarbichambi (Bolivia), 1 appears to be a late mutation of Spirifer 

 stridtus Sow., though sufficiently distinct from it to be retained as 

 a separate species. 



It differs from Sowerby's form, chiefly in the greater expression 

 of certain marked features, which may be regarded as old-age 

 characters showing an advanced stage of development. 



A comparison of the two species shows that Sp. condor is more 

 acuminate in shape, and possesses a broader area and more fully- 

 developed median fold and sinus, which are strongly marked off from 

 the lateral portions of the shell. The fold is evenly rounded, its 

 steep sides never meeting in an angle, as is commonly the case in 

 Sp. striatus. The growth-lines are very numerous and strongly 

 marked, and, crossing the well- developed ribs, produce a character- 

 istic lamellate surface, aptly described by Chernyshev as resembling 

 a tiled roof (dachziegelf ormige Zuwachslinien). 



Spirifer condor has frequently been regarded as identical with 

 Sp. eameratus Mart., but differs from it in the absence of the 

 strongly-marked grouping of the ribs into bundles which is so 

 characteristic of that species. 2 



A closely-related form, but also differing in the presence of 

 marked rib-bundling, is Sp. musaJcheylensis Dav., fine examples 

 of which are figured by Waagen 3 from the Prodnctus Limestone 

 of the Salt Range. This species agrees Avell with the Bolivian one 

 in the strongly-lamellate character of the ornament and the 

 marked development of the median fold. 



Spirifer condor has also been described by Chernyshev from 

 the ' cor a ' and ' Schwa gerina ' horizons (Pernio -Carboniferous) 

 of Timan and the Urals. 4 



Seminula ambigua Sow., mutation = S. peruviana (D'Orb.). 

 (PL VIII, figs. 3 a-S c.) 



This species seems to be well represented, both in the Titicaca 

 region and in other more southern localities. The specimens are 

 well preserved, and in the silicified examples from San Pedro the 

 internal spires are frequently visible. The shells show somewhat 

 wide variation in shape, but the most extreme types are insensibly 

 connected by intermediate forms, and all maybe referred to the one 

 species. 



1 ' Voyage dans l'Amerique Mcridionale : Paleontologie ' 1842, pp. 46-47 

 t t pi. v, figs. 11-14. 



- See J. Hall, 'Nat. Hist, New York: Palaeontology, vol. viii, pt. 2 (1894) 

 Introduction to the Study of Palaeozoic Brachiopoda ' pi. xxxii, figs. 9-15. 



•• ' Salt Range Fossils ' Pal. Indica, ser. 13, vol. i (1887) p. 512 & pi. xlv. 



4 Mem. Com. Geol. Russie, vol. xvi, No. 2 (1902) pi. xii, figs. 1-2, & pi. xxxviii, 

 figs. 1 2. 



