176 E. Billings—Structure of Oboklla ch 



6. That during this period these spots have been larger, 

 darker, and more numerous than I have before seen them, 



7. That the veiled spots are scattered throughout all lati- 

 tudes, though more complicated in the regions where the ordi- 

 nary spots make their appearance. 



8. That I have observed spots at least within 10° of the north 

 pole of the sun, 



9. That the flocculent objects sometimes seen projected upon 

 the umbra and penumbra of spots are the remaining portion of 

 the granulations composing the chromosphere, more or less dis- 

 solved by the forces emanating from the interior of the photo- 

 sphere. 



Cambridge, October 1, 18t5. 



The genus Oboklla was founded in 1861 * on the following 

 three species of Brachiopoda : 



1. 0. chromatica, discovered by J. Richardson in 1861, at a 

 place called "L'Anse au Loupj" on the north shore of the 

 Straits of Belle Isle, in Labrador, 



\ Hall, from Troy, in the State of New York. 

 0.i>o^^Va Hall, from Wis' ' 



-Ventral valves. Theb 



I * \\ i^'ig. A. — Diagram snowing wi' 

 f I tion of the scars in the dorsal ^ 



The specimens exhibited the internal characters very imper- 

 fectly, yet enough was seen to convince me that the genus was 

 a new one. During the fourteen years that have elapsed, I 

 have received a number of letters, from both American and 

 European authors, inquiring for more complete details of the 

 structure of 0. chromalica, wHch has always been considered 

 to be the type. This information I was unable to give, for 

 want of the facts. We are now in possession of specimens 

 showing the interiors of both valves, almost completely. The 

 following are the characters as nearly as they can be made out : 



In the ventral valve there is a groove in the hinge line, for 

 the passage of the pedicel. On each side of the groove there is 

 a small, somewhat deeply excavated cardinal scar. In the 

 cavity of the valve there are two elongated scars, which extend 



