54 McMahon 8^ Eudkston — 



6. Spirifer disjunotus, Sowerby. (PI. II : Ehomboidal variety, 

 Figs. 9a-c, 10.) 



Spirifera disjuncta, Sow. : Trans. Geol. Soc, ser. ii, vol. v, pi. liv, figs. 12, 13, 



and explanation of plate. 

 Spirifer disjunctus, Sow. : Davidson, Q.J.G.S., vol. ix (1853), p. 354, j)l. xv, 



figs. 1, 2, 4 ; ibid., Brit. Dev. Brach., p. 23, pi. v, especially figs. 1, 4, 



and 5. 

 Spirifer Verneuili, Murchison : Kayser in Eichthofen's China, Bd. iv, p. 88, 



pi. X, fig. 3. 



Width of the larger figured specimen (Figs. 9a-c) 34 mm. ; 

 length 26 mm. This gives the width to length as 3 : 2 approximately. 

 Shell rhoraboidal, narrowing towards the anterior margin so as to 

 produce a curved outline ; valves moderately convex. The sulcus 

 and mesial fold are moderately developed, and carry nearly the 

 same ornaments as the rest of the shell (faintly seen in the 

 specimen owing to attrition). These ornaments consist of from 

 50 to 55 regular and equidistant costse. Hinge area wide and 

 triangular, the ventral valve greatly overlapping. 



(Quadrate variety, Figs. 11, 12a-c.) 

 This variety is shown on Davidson's plate in the Q.J.G.S. by the 

 figs. 3 and 5, and in the Brit. Dev. Brach. on pi. v, fig. 6, 



Eatio of width to length very nearly as 1 : 1. Shell quadrate, 

 valves usually somewhat tumid. Sulcus in ventral valve wide 

 and not very deep ; fold on the opposite valve correspondingly 

 wide ; ornaments the same throughout. Area moderately wide 

 and trigonal in shape ; beak of ventral valve considerably produced 

 and incurved. 



There are about half a dozen specimens of the rhomboidal form 

 in the collection from Chitral, and rather more of the quadrate 

 form, together with some which may be deemed intermediate. 



The geographical distribution of this species is interesting. 

 Davidson's specimens were described from Kwang-si, a province 

 in the south of China. Herr Kayser's illustrations of this species 

 occupy more than half of a quarto plate from collections made by 

 Eichthofen in south-west China. 



7. Spirifer, species. (PI. Ill, Figs, la-c.) 

 Shell ovate: width to length rather less than 3:2. Ventral 

 valve very tumid, and with umbo considerably incurved ; area small 

 and closed. Sulcus and mesial fold not very conspicuous. The 

 ornaments consist of numerous fine radial strise. 



The restricted area and fine radial stri^, together with its ovate 

 form, seem to separate this from the disjunctus-gxow^. There is 

 only one specimen, somewhat indifferently preserved. The internal 

 mould, which is partly exposed, consists of a very black and probably 

 impure limestone, the shell itself being constituted of a brownish 

 calcite. 



8. Athyris ooncentrica. Von Buch. (PI. Ill, Figs. 2a-c.) 



Terelratula ooncentrica, Von Buch: Ueber Terebrateln, p. 103, Berlin (1834). 

 Athyris concentrica, Von Buch : Brit. Dev. Brach., p. 14, pi. iii, figs. 11-15, 24. 



