24 BRITISH CARBONIFEROUS BRACHIOPODA. 



Obs. Professor Phillips describes this species with " a lower (ventral) valve swollen 

 near the beaks, and produced in a mesial furrow receiving the angular ridge of the upper 

 valve; radiating ribs small, duplicate. Loc. Greenhow Hill." The figure published in 

 the ' Geology of Yorkshire ' is very unsatisfactory ; but, having received the loan of the 

 original specimen, I have drawn it correctly in PI. IV, fig. 15, so that no doubt may exist 

 regarding its identification with the perfect example, fig. 16, in the possession of Mr. 

 Wood, of Richmond. Professor Phillips's specimen is very incomplete and fragmentary 

 but still exhibits the characters of the species ; and what gives his figure such an 

 extraordinary beak is, that the valves were widely separated while the shell was filling 

 with matrix, so that, in addition to the real beak, a larger portion of the ventral valve 

 is seen than would have been the case had the valves been closed. In fig. 15" I have 

 given a profile view of the specimen, to satisfy the reader of the correctness of this 

 assertion. 



I have been able to examine six individuals of this remarkable shell, but they did not 

 all possess the elongated shape figured in our plate. Some were much shorter and 

 transverse, as will be seen from the measurements already given, and selected from two 

 extreme examples. Its ponderous shape, shorter hinge-line, and smaller ribs distinguish 

 it from Martin's Sj). striata. 



Loc. Greenhow Hill, and Wensleydale, Yorkshire. 



Spirifera duplicicosta, Phillips. Plate III, figs. 7 — 10; Plate IV, figs. 3, 5 — 11. 



Spirifera duplicicosta, Phillips. Geo!, of Yorkshire, vol. ii, p. 218, pi. x, fig. 1, 



1836. 



— fasciger, Keyserling. Wissenschaft Beobach. Petcbora Land., tab. viii, 



fig. 3. 



— fasciculata, M'Coy. British Palaeozoic Fossils, tab. hi d, fig. 25, 1855. 



Spec. Char. Transversely sub-rhomboidal when adult, longer than wide, or almost 

 circular when quite young ; valves moderately convex, with a more or less produced 

 mesial fold in the dorsal, and a corresponding sinus in the ventral one. The hinge- 

 line is shorter than the width of the shell, the area of moderate breadth, beak incurved. 

 Valves ornamented by numerous radiating ribs, which rapidly augment at various distances 

 from the beaks by intercalation as well as bifurcation. Two examples have afforded the 

 following measurements : 



Length 16, width 20, depth 11 lines. 

 „ 16^, „ 17£, „ 10^ lines. 



Obs. Professor Phillips describes his species with " mesial fold angular ; radiating 

 ribs numerous, duplicate towards the margin." No form is, however, more variable than 

 the one under description, both as to shape, dimensions, and character of plication ; and 



