Vol. 51.] OF THE MID-COTTES WOLDS. 451 



Lastly, the lateral folds are more curved in the opposite direction 

 to the mesial fold, so that the mesial fold is longer ; there is a con- 

 cave curve between the rostrate part of the perforate valve and the 

 edge of the lateral fold, and the shell becomes altogether more 

 angular. 



These characters are borne out not only by the figures of the 

 authors mentioned, but by a large series of specimens in my cabinet. 

 They vary, of course ; for instance, in the prominence of the mesial 

 fold and its liability to be rectangular to the lateral fold, as noted 

 above ; but no specimens of a considerable series of the preceding 

 species attained to anything like rectangularity. Thus, while lines 

 from the beak to the lateral and mesial folds over the respective 

 valves may give in this species an angle of about 87°, no specimens 

 of the preceding species show more than about 65°. 



Rh. cynoprosopa occurs in the Cephalopoda-bed of the Cottes- 

 wolds ; and it lived during the Dumortierice hemera. It is found at 

 Haresfield Hill and Standish Beacon — plentifully, but of rather 

 small size, in a bed of brown earthy marl, larger but scarcer lower 

 down, with Terebratula haresfieldensis ; also at Standish Park, at 

 Coaley Peak, and other localities. Like the last species, it shows 

 1- and 3-plait varieties, but these are very rare ; the 2-plait form 

 greatly preponderates. 



PtHYETCHONELLA CYSTICA, 1 Sp. n. 



1882. Rhynchonella Beneckei, S. Buckman (non Haas), ' Brach. Inf. Ool.,' Proc. 

 Dorset Nat, Hist. & Ant, Field-Club, vol. iv. p. 51. 



1884. Rhynchonella Beneckei, Davidson, App. to Suppl. ' Monogr. Brit. Fossil 

 Brachiopoda,' vol. v. pi. xx. figs. 8-10, Pal. Soc. 



Rhynchonella cynocephala, auct. 



A Rhynchonella somewhat like cynocephala. The mesial fold 

 broad, not much elevated, bi- or triplicate, sometimes quadri- 

 plicate. 



I cannot defend my identification of this species with the Rh. 

 Beneckei, Haas & Petri 2 — an identification considered by Davidson 

 as very uncertain (op. cit. p. 274), although he figured it by that 

 name. It therefore becomes necessary to give it a new designation. 



The present species is not unlike a somewhat large edition of 

 Rh. cynocephala, though it differs — not only in being always of much 

 larger size, but in the greater coarseness of its ribbing, as well as 

 in the broader, more deeply and broadly-divided mesial fold. From 

 Rh. cynoprosopa the coarser ribs, the broader and much less elevated 

 mesial fold easily separate it. 



The number of ribs on the mesial fold is variable, but in this 

 respect the present species differs from Rh. Stephensi or Rh. cyno- 

 prosopa. Those species show a great preponderance of forms with 

 2 plaits on the fold, rarely forms with 1 and 3 plaits. The present 

 species shows mostly forms with 2 and 3 plaits, rarely varieties with 



1 KwtKi)?, dog-like. 



2 A correction ia the text altered the name to Eh. delmensis, H. & P. 



