THE LOWER EMBAR OF WYOMING 655 



As considerable doubt has recently been expressed concerning tne 

 age of much of the so-called Permian of Texas, it is not safe to give 

 the range of this species as extending into the Permian without 

 more specific data. 



Eunemacanthus keytei n. sp. (PL IV, Fig. 1, and Text-Fig. 1) 



The preserved part of this spine is only 35 mm. in length but 

 includes parts of both exserted and inserted portions. The pulp 

 cavity is small and completely inclosed. The front of the spine 

 is formed of one rounded enameled ridge. Next to the inserted 



Figs. 1-6. — (1) Cross-section of spine of Eunemacanthus keytei Branson; (2) cross- 

 section of spine of Ctenacanthus obscuracostatus Branson, at base of preserved part; 

 (3) cross-section of spine of Ctenacanthus obscuracostatus Branson, at outer end of 

 preserved part; (4) cross-section of spine of Batacanthus gigas Branson, at outer end 

 of preserved part; (5) cross-section of spine of Ctenacanthus amblyxiphias Cope; 

 (6) cross-section of spine of Ctenacanthus browni Branson. 



part, one side has 9 broad, flat-topped ribs, and the other 8 such 

 ribs. The space between the ribs is narrower than the ribs, flat- 

 bottomed, and marked with longitudinal striae formed by the out- 

 cropping of longitudinal pores. The ribs increase downward by 

 bifurcation and probably by implanation. The back of the spine 

 is convex and is marked by about 25 striae formed in the same way 

 as those between the ribs. The spine tapers rapidly and the 

 exserted part seems to have been about 10 cm. long. 



This form differs from E. costatus N. and W. 1 in tapering more 

 rapidly and in the convexity of the back. 



The species is named for I. Allen Keyte, of Colorado Springs, 

 Colorado, whose untiring zeal- in collecting added many specimens 

 to the cabinets of the University of Missouri. 



1 Geol. Surv. Ill, VII, PL XXIII, Fig. 2. 



