NUCULANA LjEVISTRIATA. 205 



Orchard Quarry, Upper Limestone series, a locality in which the species under 

 description also occurs. This author, too, has mistaken the anterior for the 

 posterior extremity. In his description he says, "anterior side short, much 

 smaller than the posterior, bluntly attenuated ; posterior side elongated, inclined 

 to become square, but with the margin uniformly rounded." He points out that 

 his shell resembles N. brevirostris, but says " it has a much straighter dorsal 

 margin anteriorly, and a less constricted anterior end." He is quite right in this 

 observation, because this is the condition which obtains in the youug shell. Mr. 

 Bennie has kindly sent me several specimens of all stages of growth, and these 

 illustrate well the changes which take place in the shape of the shell during 

 adolescence. PI. XV, fig. 31, is from the quarry whence the type of N. Youngiw&s 

 obtained. I have figured a series of shells of this species, PI. XV, figs. 

 26 — 31, to show the different stages of growth and the identity of N. Youngi, 

 Eth., and N. brevirostris, Phill. The well-marked escutcheon shows dis- 

 tinctly the real affinity of this species with Nuculana, and also indicates the 

 posterior end. 



The figures referred to N. cuneata, Phillips, by de Ryckholt (as Leda) belong 

 distinctly to the species under discussion. I am of the opinion that N. cuneata, 

 Phillips, does not belong to the genus Nucula, from an examination of the type 

 specimen preserved in the Grilbertson Collection in the Brit. Museum (Nat. 

 Hist.). 



Unfortunately Hall gave the name " brevirostris'' " to a shell from the Hamilton 

 group (Devonian) of New York, which has no specific similarity to the British 

 form ; and as Hall quotes himself as the author of the specific term, he was 

 evidently unaware of the previous use of the name. Hall's shell closely resembles 

 N. stilla, M'Coy, in general shape. 



Nuculana l^vistriata, Meek and Worthen, 1860. Plate XV, figs. 39 — 43. 



Leda (Yoldia ?) l^ivistbiata, Meek and Worthen, 1860. Proc. Acad. JNat. Sci. 



Philadelphia, p. 457. 

 Yoldia ? l.s;vistriata, Meek and Worthen, 1866. Geol. Surv. Illinois, vol. ii, 



p. 282, pi. xx, figs. 7a, b. 

 Leda. intermedia, B. Etheridge,jun., 1873. Geol. Mag., vol. x, p. 347, pi. xii, 



fig. 3. 

 — — — — Mem. Geol. Surv. Scotland, Expl. 



Sheet 23, p. 105 (no figures). 

 Cf. Yoldia Stevensoni, Meek, 1875. Geol. Surv. Ohio, vol. ii, p. 335, pi. xix, 



figs. 4 a, b. 

 — l^visteiata, Bigsby, 1878. Thesaur. Devonico-Carboniferus, p. 314. 



