14 NEW YOHK STATE MUSEUM 



The form found at Ryeedorpb hill proved, by thin sections, to 



be a Prasopora, identical with Prasopora s^m u 1 a t r i x 



Ulrich, and very probably representing his var. o r i e n t a 1 i s , 



which is common in the Trenton limestone of Trenton Falls and 



Of 1 own. (Oroiip IS) 



BRACHIOPODA 



siPHONOTRETA de Vemeuil 



Siphonotreta minnesotensis Hall & Clarke. Pal. N. Y. 1892. v. 8, 



pt 1, p. 177 



PI. 1, fig. 4, 5 



A single but well preserved pedicle valve of a species of 

 Siphonotreta was found in a pebble of black compact lime- 

 stone associated with cranidia ofPterygometopus Gal- 

 lic e p h a 1 u s . 



As only two species on this continent have thus far been 

 referred to Siphonotreta, i. e. S. (?) micula McCoy from the 

 Beekmantown horizon of Canada, and S. (?) m i n n e s o t e n s i s 

 Hall and Clarke, from the Stones river beds of Min- 

 nesota, and as our form agrees with the latter species 

 in all important features, it seems advisable to refer this valve 

 at present thereto. Of both of these species the pedicle valve 

 is completely known, and, on this account, their relation 

 to the European genus Siphonotreta is still doubtful. The 

 specimen from Rysedorph hill supplies this desired information 

 for Siphonotreta minnesotensis. 



The pedicle valve found is broadly eubovate in outline, 

 depressed convex, with a straight, elevated, at first conic, but 

 terminally cylindric beak, rising a little posteriorly of the center 

 of the valve and extending beyond the cardinal margin. Beak 

 perforated, foramen round and apical. Median part of shell 

 depressed, lateral parts low, convex, increasing rapidly in slope 

 toward the lateral margin. Surface of the umbonal region 

 nearly smooth, with faint concentric wrinkles which rapidly 

 increase in strength anteriorly. From the wrinkles proceed 

 numerous straight, thin spines, which attain the full length of 

 the shell, extending far beyond the anterior and lateral margins. 



