204 



THE CARBONIFEROUS SYSTEM. 



(1.) Naiadites (Anthracoptera) carbonaria (Dawson) — Fig. 42. — 

 Hinge-line straight, more than one half the length of the shell ; beak 



Fig. 42. 



Figs. 42 to 46. — Species of Naiadites. 

 Fig. 43. 



Fig. 45. 



Fig. 46. 



acute, in the anterior fourth of hinge-line ; anterior margin abruptly 

 rounded ; ventral margin nearly straight, with a slight sinus ; posterior 

 margin broad and regularly rounded ; shell thin, with distinct growth 

 lines. When recent, the shell was probably somewhat tumid, but is 

 usually flattened, and often much distorted by pressure, so that it is 

 very difficult to obtain a specimen sufficiently perfect to be described 

 or figured. Length of adult, an inch or more. This is the most 

 abundant species in the Coal measures of the Joggins, beds of some 

 thickness being often almost entirely made up of the valves. Fig. 31, 

 p. 182 supra, represents an imperfect and distorted specimen. See 

 also Fig. 22 in my paper on the South Joggins in the Journal of 

 the Geological Society, vol. x. p. 39. This shell may possibly be the 

 Modiola Wyoming ensis of Lea (Journ. Ac. Nat. Science, 2d series, 

 vol. ii.) ; but if so, his specimen is imperfect. 



(2.) Naiadites (Anthracomya) elongaia (Dn.) — Fig. 43. — Smaller 

 than the preceding, and more elongated laterally ; the beaks obtuse 

 and more anterior; the hinge-line nearly straight and less than half 

 the length ; ventral margin slightly compressed ; length, half an inch 

 to an inch ; common at the Joggins and Sydney, in the Middle 

 Coal measures. See Fig. 23 in paper above cited. 



(3.) Naiadites [Anthracoptera] laevis (Dn.) — Fig. 44.* — Broad 

 ovate, extremely thin ; beak about one-third of distance from anterior 

 end. This species is smaller, more rounded, thinner, and with the 



* Mr Salter thinks that this is identical with a species found in the Upper Coal 

 measures of Manchester. 



