52 On the Permian System of Durham and Northumberland. 



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. 



13. Spiriferina cristata, Schloth. — It is more sharply 

 triangular than any other Permian species occurring in this 

 district. It is also well characterized by the sharpness and 

 depth of its numerous plaits and the great size of the perfora- 

 tions of the shell. 



It is rather sparingly distributed, occurring mostly at Hum- 

 bleton and Tunstall in shell-limestone. 



14. Spiriferina multiplicata. Sow. — It is very much 

 rounded in its general outline, and the plaits are less nume- 

 rous and more rounded than in the foregoing species. The 

 shell-punctures are very much smaller, so as not to be visible to 

 the naked eye or impressed on casts. The T, Jonesiana, King, 

 is only a more rounded form of this shell occurring commonly 

 at Dalton. 



It occurs rather plentifully in the shell-limestone of several 

 localities. 



15. Spirifer undulatus. Sow. — I regret that I cannot 

 assent to the division of this fine characteristic shell into three 

 species, as proposed by Mr. King in the * Permian Monograph/ 

 The specimens figured in this work, pi. 10, are all referable to 

 the above, and in the text no character has been pointed out of 

 specific or even varietal value. 



It is not very abundant in any locality, but may be met with 

 most frequently at Humbleton in the shell-limestone. It occurs 

 also in the compact limestone and in the magnesian conglomerate 

 at Tynemouth. 



16. Terebratula elongata, Schloth. — I agree fully with 

 Dr. Geinitz, who has referred all the forms, including T, sufflata, 

 occurring in the magnesian limestone, back to this species ; and 

 I deeply regret that the author of the 'Permian Monograph^ has 

 again attempted to raise the T. sufflata to the rank of a species, 

 for surely nothing can be so injurious to the true progress of 

 science as the burdening of it with useless synonyms. 



This species is very abundant in several localities in the shell- 

 limestone, of which it is very characteristic. It occurs at Tyne- 

 mouth, in the magnesian conglomerate. 



[To be continued.] 



