482 GEOLOGICAL SURVEY OF IOWA. 



S TAXOCRIMIS (PHILLIPS). 



BASAL plates five, small ; radial plates three in five series ; 

 arms subdividing upon the third radial, and frequently 

 dichotomizing above this point ; arms and branches com- 

 posed of a single series of joints. Interbrachial and axillary 

 plates. 



The definitions and illustrations of this genus, which have fallen under my obser- 

 vation, are not as clear as could be desired; and it is evident that the genus, as 

 recognized in Great Britain, contains a heterogeneous assemblage of species. 



PICTET has selected the Cyathocrinus tuberculatus of MILLER as the type of this 

 genus; and following the characters there presented, I believe the following species 

 may be placed under the same designation, though presenting some slight differences. 

 GOLDFUSS, in his fig. A, pi. ~,8*, represents a double interradial plate truncating the 

 upper angle of one of the basal plates; but in the enlarged figure, this plate is re- 

 presented as lying between the second radials and resting on the sloping edges of two 

 adjacent first radials. The figure of PICTET is like the first named figure of GOLD- 

 FUSS, while the figure in MUBCHISON'S Silurian System represents the interradial 

 plate as in the fig. B of GOLDFUSS. 



Taxocrimis interscapularis (n.s.). 



PLATE I. FIG. 3. 



BODY narrow, turbinate below the first bifurcation of the 

 arms : basal plates five, short, with the angular summit 

 much pointed upwards between the lower radial plates ; ra- 

 dial plates three in each series, much wider than high, the 

 two lower series quadrangular ; upper radial broad pentago- 

 nal, with the two upper sloping sides supporting a double 

 series of arm-plates ; interbrachial plate narrow, resting the 

 base slightly on the second radial plates, with its upper ex- 

 tremity lying between the second arm-plates. 



Arms ten ; those on the exposed side bifurcating on the 

 fifth plate above the base, and the adjacent parts again bi- 

 furcating upon the eighth and tenth plates respectively, 

 while the outer divisions of the same arms continue simple 



* Petrefacta Gftrmanise, plat* Iviii. 



