102 CARBONIFEROUS LAMELLIBRANCHIATA. 



Dimensions. — Fig. 10, PI. VII, measures — 



Antero-posteriorly (greatest across the lower third of the shell) 14 mm. 

 Dorso-ventrally . . . . .14 mm. 



Elevation of valve . . . . .3 mm. 



Localities. — The Bullion Mine, near Halifax, Colne, and New Hey, near 

 Rochdale. 



Observations. — I have been able to obtain access to only three specimens of 

 this species, one of which (fig. 10, PI. VII) is in the Owens College, and is the 

 property of Professor W. Boyd Dawkius ; one is in my own collection, and was 

 obtained from Mr. Stock, of Bristol ; and the other is a cast of the exterior on a 

 small bullion from Colne. These specimens show the radiating lines over the 

 posterior portion of the shell, and the short hinge-line. 



Captain Brown's Gatillus costatus is said to have " numerous very flat, 

 longitudinal, diverging lines of growth ;" but is " oblong-ovate " in shape ; and I 

 can find nothing in his collection at all like the species under description. The 

 species marked G. costatus I have referred above to P. Kirhmani. The narrow 

 hinge-line, general shape, and radiating lines are characteristic of this form, 

 which approaches more closely to P. pyriformis of the Mountain-limestone of 

 Settle than to any of the other forms. 



Sub-family DREISSENNIN^, StoliczJca, 1871. 



Genus Naiadites, Dawson, 1860. 



(See the Monograph on " Carbonicola, Anthracomya, and Naiadites," Pal. Soc, 1895, p. 126.) 



Generic Description. — Shell modioliform, obliquely triangular, inequivalve ; 

 anterior end lobed ; umbones not terminal. Hinge-plate thickened, with many 

 transverse striations, with an obscure cardinal tooth in front. 



Anterior muscle-scars trifid and pit-like. Posterior adductor scar large, situated 

 near the posterior border. Pallial line non-sinuate. 



Species], Naiadites hodiolaeis, Sowcrly, sp., 1840. Op. supra cit., p. 131, pi. xvii, figs. 



8—10, 12—30. 

 ,, 2. — teiangulaius, Soic, sp., 184.0. Op. supra cit., p. 135, pi. xvii, 



figs. 31—38. 

 „ 3. — caeinata, Sow., sp., 1840. Op. supra cit., p. 138, pi. xviii, figs. 



1—16. 

 „ 4. — quadeata, Sow., sp., 1840. Op. supra cit., p. 140, pi. xviii, figs. 17 — 



21, 23—25. 

 „ 5 — elokgata, Hind, 1895. Op. supra cit., p. 142, pi. xviii, figs. 22, 



26—35. 



