part 2] SYRIXG0THY1US A>D SPIBIFERINA. 218 



laterally to a point a little anterior to the cardinal extremities ; 

 the jugum is .slender, and forms a shallow V-shaped process, with 

 its apex directed ventrally and posteriorly. 1 



Range. — (As at present determined) Carboniferous Limestone. 3 



Grenotype. — P. scabricosta, sp. nov. 



Remarks. — This genus differs from Spiriferina in the greater 

 number of its costa?, which are smaller and less angular, in the 

 greater relative size of its fold and sinus, and in its jugum. From 

 Tylotliyris it differs in its punctate shell-substance, and in the 

 absence of a well-developed apical callosity. 



Ptdjctospirifer scaericosta, sp. nov. (Text-figs. 1 p, 4 7/, 5f, 

 & 5g, pp. 166, 199, 211 ; PI. XIII, fig. 6.) 



1912. Spiriferina laminosa (M'Coy), Garwood [13] p. 572 & pi. li, figs. 7a-7e. 



Description. — Shell spiriferoid, of medium size, greatest 

 width a little below the hinge-line. 



Pedicle-valve subpyramidal, cardinal area about a third as 

 high as wide ; concave, especially towards the beak which is small 

 and pointed ; apical angle about 110°, delthyrial angle 40° ; sinus 

 shallow (width about three times the depth). 



Brachial valve convex, median fold narrow at the beak, 

 rounded, and strongly defined anteriorly. 



Each lateral slope in both valves bears from seven to ten simple 

 rounded costse, separated by rounded furrows, and crossed by a 

 strong concentric lamellar ornament. 



Internal structures: — Pedicle - valve. Delthyrial sup- 

 porting-plates attached to the floor of the valve for about a third 

 of its length ; median septum attached to the floor of the valve 

 for half its length, thickened at the base, and tapering rapidly 

 upwards ; no apical callosity. 



The dimensions of an average specimen are- — width along hinge- 

 line, 20 mm.; length of brachial valve, 12 mm.; height of area, 

 10 mm. 



Holotype. — A specimen from the Ashfell Sandstone (lower 

 part of the T? roduct us-corruyato-liemispliericus Zone, S) of the 

 Raven stonedale district, in the collection of Prof. E. J. Garwood; 

 figured, Q. J. G. S. vol. lxviii (1912) pi. li, figs. 7 a-7 e. 



Comparison with Tylotliyris laminosa . — The more 

 obvious differences between this species and T. laminosa (namely, 

 the punctate shell-structure and the absence of an apical callosity) 

 have already been mentioned. It is further distinguished by the 

 fact that the shells are usually much smaller than the representa- 

 tives of T. laminosa and T. subconica, which occur in the Upper 

 Avonian strata. 



1 The jugum as seen in a specimen rubbed down for the purpose is strikingly- 

 similar to, but rather less angular than, that described by Hall & Clarke [14] 

 p. 54, as occurring in Spiriferina Kentucky ensis, which in external appearance 

 also has much in common with the genus under consideration. 



2 But it is highly probable that the genus includes species in Permian and 

 even later formations. 



