OP THE PURBECK 70RMATI0^^. 341 



Cijpridea granulosa and C. fasciculata, H. Woodward, Catal. Poss. 

 Crust. 1877, p. 88. 



Cypindea verrucosa (var.), Jones, Geol. Mag. dec. 2, vol. v. 1878, 

 p. 108, pi. 3. fig. 6. 



Length 1 mm. 



Siiboblong or broadly obovate ; anterior end obliquely and boldly 

 rounded, posterior somewhat narrower and nearly semicircular; 

 hinge-line slightly oblique, having the front hinge-joint at an 

 obtuse angle. Beak and notch not always strongly developed. 

 Contact-margins flanged and furrowed, nearly continuously, and 

 subject to difference of intensity in individuals. Edge- view of 

 carapace narrow-ovate ; end-view oval. The surface punctate, and 

 also granulated. The pitting consists of either subcircular pits, as 

 on a thimble, or minute suboblong pits, almost forming a reticulate 

 pattern. In no cases that I have seen are the granules distributed 

 over all the surface, the median region always having fewer (as in 

 Sowerby's figure 4, pi. 21, in Pitton's Memoir), and often none (see 

 PI. YIII. fig. 18). The granules are always grouped in two sets or 

 fascicules, one on the anterior and one on the posterior third of 

 each valve; hence the appropriate name '■'■ fasciculata^^ given by 

 E. Porbes to this dominant Mid-Purbeck species. The number of 

 granules in these local groups is variable, as above intimated. 

 Sowerby's type-figure has many granules, some coming near to the 

 middle of the valve; other specimens collected by Pitton, and 

 labelled with Sowerby's name, have very few granules. There is 

 no line to be drawn, so far as essential characters are concerned, 

 between the multigranulate and paucigranulate modifications ; 

 but it will be convenient to recognize the varieties. In the Mid- 

 Purbeck beds of Durlston Bay both abound, and at Teffont (^o. 

 38), the multigranulate forms predominate. At Dashlet (also in 

 the Yale of Wardour), and at Whitchurch, in Bucks, the pauci- 

 granulate variety occurs plentifully (figs. 8-20). In specimens 

 (M.P.G.XbJ) from the Mid-Purbeck of Durlston Bay the valves 

 are mostly paucigranulate ; one, at least, has the hinder fascicule 

 obsolescent. They have a coarsely punctate or subreticulate surface. 

 Some strong, squarish, convex individuals from Dashlet have very 

 few tubercles, only five, or even four, in the fascicules ; and the 

 punctation takes on a partially regular pattern, the pits on the 

 anterior half of the valve being oblong and even elongate, curving 

 round in front and radiating backwards for a little way from the 

 anterior group of five granules. Even without regarding the modified 

 punctation, these specimens may be looked on as a variety, paud- 

 granulata ; whilst the ordinary multigranulate forms divide them- 

 selves into the common variety fascicidata (Porbes), and the rarer 

 and earliest named granidosa of Sowerby with the granulation 

 covering almost the whole surface. The name fascicidata has been, 

 and still continues to be, convenient for general use. 



C. granidosa (Sow. in Pitton, pi. 21, fig. 4, of Pitton's Memoir), 

 is decidedly the fascicidata of E. Porbes, and its localities are there 

 given (p. 260) thus : — " Between DaUard's Parm and Catharine 



Q. J. G. S. No. 163. 2 b 



