82 Description of Genera <xiid Species. 



Crangopsis ilastata sp. nov. PI. XL, figs. 19, 20. 



Remarks. — Among the material obtained by Mr. Ehodes from the Cementstone 

 Group of the Lower Carboniferous rocks of Eedesdale, Northumberland, there are the 

 tail fans of what appears to be a species in which the telson, while having a strong 

 general likeness to those of the present genus, and more particularly to those of the 

 second group into which it is divisible, differs considerably from any as yet described. 

 The difference is one of degree and not of kind, for it consists chiefly in the greater 

 elongation of the terminal lobe, which is produced into a spear-shaped protuberance as 

 long as the body of the telson. Accompanying this strengthening, the accessory swim- 

 merets are longer than usual, and this general lengthening is also shared by the lu-opods, 

 especially in their terminal branches. Should further search result in the finding of 

 more complete individuals, they will in all probability be classed witli the meml)ers of 

 the second group, wherever that may be placed. 



The specific name is suggested from the shape of the projection of the telson. 

 Fig. 19 shows the tail fan from alcove. Fig. 20 is from a specimen seen sideways and 

 from beneath ; both magnified about 4 diameters. 



Locality. — Chattlehope, Eede Water, Northumberland. 



Horizon. — Cementstone Group (Tuedian), (Scottish) Calciferous Sandstone Series. 



Collector. — J. Ehodes. 



The species of the genus Crumjopsis as constituted in this memoir naturally fall 

 into two groups, viz. : — 



I. Those in which the epimera of the second tail segment are large and rounded, 



and overlap on to the epimera of the segments both in front and 

 behind it, including the following species: — (1) Cramjopsis socialis Salter 

 (type) ; (2) C. eskdalensis (Peach) ; (3) C. huxleyi (H. Woodward) ; (4) 

 C. clegans (^Peach). 



II. Those in which the epimera oi the second segment are more or less pointed 



and only overlap backwards on to those ot the succeeding segment, includ- 

 ing the species (5) C. couttsi Peach ; (B) C. rhodesi Peach ; (7) C. magna 

 Peach; (8) (\ robusta Peach; (9) C. minuta Peach; and probably (10) 

 C. hdstata. Peach. 



