PALiEONEILO. 141 



Palaeoneilo, Hall, 1870. Prelim. Notice Lamellibr. N. Y, pt. ii, p. 6; 1882, 

 Whitfield, Ann. N. Y. Acad. Sci., vol. ii, p. 217; 

 1885, Hall, Pal. N. Y., vol. v, pt. i, Lamellibr. ii, p. 

 xxvii ; 1887, Fischer, Man. de Conchyl., p. 984 ; 1888, 

 (Ehlert, Bull. Soc. gcol. France, ser. 3, vol. xvi, p. 653, 



Ctenodonta, pars, Beushausen, 1895. Abhandl. Konigl. Preuss. Geol. Landesanst., 

 ser. ii, pt. xvii, p. 65. 



Palaeoneilo, Hind, 1900. Quart. Journ. Geol. Soc, vol. lvi, p. 46. 



Generic Characters. — " Nuculiforra shells, transversely ovate or subelliptical, 

 the posterior end often subrostrate, with a more or less defined sulcus along the 

 umbonal slope. Cardinal line arcuate. Surface marked with strige of growth, 

 which are often lamellose and elevated into concentric ribs. Hinge furnished with 

 a row of regular small transverse teeth, which is sometimes interrupted beneath 

 the beak by a change in the direction of the teeth, or by several oblique teeth. 

 Ligament external, contained in a shallow and narrow groove along the cardinal 

 border. Muscular scars not strongly impressed, situated below the extremities of 

 the hinge-line. Pallial line simple." 



Observations. — The genus Palaeoneilo was established by Hall for certain 

 Nuculiform shells from the Devonian beds of New York. He selected as the 

 type Palseoneilo constricta, which had hitherto been referred to the allied genus 

 Wuculites by Conrad. Hall referred twenty species to this genus. 



Palseoneilo differs from Nucula and Nuculana in possessing no internal 

 cartilage-pit, situated beneath the umbo, and between the anterior and posterior 

 lines of teeth. From Nuculites it also differs by having the row of hinge-teeth 

 interrupted below the umbo, and by having no shelly process (the clavicle) 

 separating the anterior adductor muscle-scar from the rest of the valve. Cteno- 

 donta, however, is much more nearly related to Palseoneilo, but the former is 

 nearly equilateral, and has no vertical comb-like hinge-teeth just below the hinge, 

 neither does it possess the characteristic radiating sulcus, on the dorsal slope, nor 

 the well-marked escutcheon. 



Beushausen has, however (op. supra cit.), referred all the Devonian shells of 

 Rhenish Prussia to Ctenodonta, considering that Palaeoneilo is nothing more than 

 a sub-group of that genus. (Ehlert (op. supra cit.), on the other hand, considers 

 Palseoneilo to be generically distinct from Ctenodonta. Whidborne 1 refers certain 

 shells to Ctenodonta (Palseoneilo). 



The Nuculidae are represented in Carboniferous rocks by the genera Nucula, 

 Nuculana, and Ctenodonta, and to these must now be added Palseoneilo. Two fine 

 examples of this genus are in the Museum of Practical Geology, Jermyn Street, 

 labelled "Carboniferous Shale (bottom of Yoredale Shale), beck south of 



1 Monogr. Palaeont. Soc, ' Devonian Fauna,' vol. iii, pt. i (1896), p. 98. 



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