274 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxviii. 



Orthi^t lenticalarisf Kayseh, Pala'ontograpliica, Priuiordiale und untersil. Foes. 



Argentinischen Rei)ublik, J I, 1876, j). 9, pi. i, figs. 11, 12. 

 Orthis lenticularis Brogger 1882, Die Sil. Etagen, 2 und 3, p. 48. 

 Orthh lenficularifi Matthew, Trans. Roy. Soc. Canada, IX, 1891, p. 46, pi. xii, 



figs. 9a-d. 

 Orthis lenticular Ik var. slrophomenoidea Matthew, Trans. Roy. Soc. Canada, IX, 



1841, p. 49, pi. XII, figs. 12a, 12b. 



Dr. George F. Matthew in his excellent review of the descriptions 

 of this species gives a translation of Wahlenberg's original description, 

 together with the Latin; also Dahnan's, Leopold von Buch's, and 

 Salter's descriptions. 



He calls attention to the fact that if the reader will compare the sev- 

 eral descriptions of this species by the authorities named he will be 

 surprised at the diversity they exhibit. This diversity, Doctor 

 Matthew thinks, is due partly to the imperfect descriptions of the 

 earlier writers, but chiefly to the remarkal)le variability of the species." 

 Doctor Matthew recognized the species in the Upper Cambrian, St. 

 John, New Brunswick, and he also distinguished three varieties. 

 Through Doctor Matthew's kindness I had the opportunity of studjdng 

 the types of the varieties. 



Through M. Schmalensee, collector of the geological survey of 

 Sweden, I secured a large and hue series of this species from thin 

 bands of limestone in the Olenus and alum shales at Olands and Nunne- 

 burg. I also collected a quantity of the shells from the Upper Cam- 

 brian of Manuels E-iver, Newfoundland. From this material an 

 attempt has been made to select a series illustrating the great range of 

 variation in form and surface markings; first, from Sweden; second, 

 Newfoundland, and third, New Brunswick, I was not able to obtain 

 satisfactory material from Wales, but Mr. Davidson's figures illustrate 

 fully the peculiarities of the species as it occurs there. These illustra- 

 tions will appear in the completed monogi-aph on the Cambrian 

 brachiopoda. 



Only one specimen was found in which the two valves were united. 

 The convexity of the two valves is subequal, the ventral being a trifle 

 greater. 



A very careful search has been made of casts of the interior to illus- 

 trate the muscle scars and vascular markings. In a few instances 

 traces have been found. One of these shows the area (pseudospondy- 

 lium) beneath the umbo of the ventral valve; also the main vascular 

 sinuses. Doctor Matthew illustrates some traces of the vascular 

 markings and muscle scars, l)ut they are almost too indefinite to be of 

 value. 



In a single specimen of the ventral valve from Olands, the cast of 

 the umbonal cavity is nearly as sharp as in some specimens of Plee- 

 torthis remnicha. The cavity is tripartite, the central division being 



"Trans. Roy. Soc. Can., IX, 1891, pp. 46-47. 



