NORTHUMBERLAND AND DURIIxiM. 257 



iible to detect the presence of spinous processes on tlie margin 

 of the coil. 



It seems to he generally admitted by English pahvontologists, 

 that the generic name Athyris, as applied to this shell, is a 

 serious misnomer ; there snrely, then, onght to he no hesitation 

 in at once throwing it overboard, especially as according to 

 Mr. Davidson the more correct one is '' generally preferred and 

 adopted with good reason on the Continent." 



In England this species is almost as limited in its distribution 

 as the last, occurring only in the shell-limestone at Humblcton , 

 Tunstall, and Hylton, and in the magncsian-conglomerate at 

 Tynemouth. 



0. MARTINIA, :)I'Coy. 



1. M. Clannyana, King. 



Through the kindness of Baron Schauroth I have lately seen 

 a specimen of this small shell on which the spines were Avell pre- 

 served, from the shell-limestone of PiJssneck, but in all the 

 English specimens that I have examined the spines are bi'oken 

 off, and the outer surface of the valves is studded all over with 

 minute granulations. 



It occurs rather plentifully at Ryhope-Field-House, and Mr. 

 Kirkby has recently taken it at Tunstall, in shell-limestone. 

 There are some specimens in the Sunderland Museum much 

 larger than any others I have seen ; they are from the compact- 

 limestone of Pallion. 



10. ^VmiFYAll1sA,<rOrhuj,nj. 



1. S. ctjstata, Schloih. 



It is more sharply triangular than any other Permian species 

 occurring in this district. It is also well characterised by the 

 sharpness and depth of its numerous plaits, and the great size of 

 the perforations of the shell. 



It is rather sparingly distributed, occurring mostly at Hum- 

 blcton and Tunstall in shell-limestone. 



