62 TRANSACTIONS OF THE [NoV. 16, 



Edestus lecontei, n. s. 



Type in the Palfeontological Cabinet of the University of 

 California. 



The fossil is shown in about its natural size in the accompany- 

 ing figure, PI. IV, Fig. 1. Its matrix, a carboniferous shale, re- 

 sembles closel}' that of Edestus heinrichsiior of E. minor — light 

 gray in color, hard and brittle. The spine is not preserved as per- 

 fectly as in specimens of other species which the writer has ex- 

 amined. Its surface bears evidence of having been somewhat 

 weathered prior to fossilization ; the enamel of the large marginal 

 denticles appears altered, and it is only at favorable points that 

 the segmented nature of the spine maj' be determined. The fol- 

 lowing characters may be described : The base (shaft) of the 

 spine is broad at one end and tapers gradually toward the other. 

 The former may therefore be regarded as the proximal end. 

 The distal termination has not been preserved, but judging from 

 contours this region of the spine may well have measured half an 

 inch longer. Where the tip has been broken off al)ruptly the spine 

 is triangular in section, PI. IV, Fig. I. A, and appears to have been 

 relativelv stout — for the proximal end was notably flattened and 

 might be represented in transverse section by a long ellipse. 

 Along the dorsal (convex) rim of the spine are arranged seven- 

 teen large denticles ; those of the proximal region are tall and 

 acutely pointed ; those of the distal end wide and short. The 

 latter bear evidence of having had rounded ends, although in 

 these portions they have not been perfectl}' preserved. Between 

 these two extreme types appear transitional forms causing the 

 line of denticles to present a graded series. p]ach of these ele- 

 ments is flattened in the plane of the sides of the shaft of the 

 spine, precisely as in E. davisii, and presents a cutting edge on 

 anterior and posterior rims. Along these cutting edges of the 

 large or primary denticles a row" of small secondary denticles 

 has not been definitel}^ determined in the present specimen, ow- 

 ing possibl}^ to imperfect preservation. It should, however, be 

 noted that at several points on the fore most primar}^ denticles 

 a peculiarly roughened margin might perhaps be interpreted as 

 a series of minute secondar3' denticles. The segmented char- 

 acter of the shaft in E. lecontei is by no means clearly marked. 

 In the proximal region the basal segments may be determined, 

 but, as shown in the present figure, they are certainly incon- 

 spicuous. Traces of them disappear entirely in the hinder re- 

 gion of the shaft. 



The relation of E. lecontei, to other species of Edestus. 

 The structural characters of Edestus lecontei differ notablj' 



