Vol. 62.] BKACHTOPOD HOilCEOMOEPHY. 449 



Genus Pygites, gen. no v., ex de Haan, MS. 1 



1833. Pugites, de Haan, MS. Mus. Lugdun., teste Bronn [2], Dall [12], et al. 

 Genotype — Terebratula diphyoides, d'Orbigny. 



A series of diphyoid Terebratuloids with the characters of Pygope, 

 except that in the preperforate stage (onto- and phylogenetic) the 

 dorsal valve carries an additional fold, and the ventral valve an 

 additional sulcus. 



Remarks. — De Haairs name is practically a nomen nudum. It 

 can take no priority ; but there is no question of that. The evidence 

 shows that he applied it as the generic appellation for diphyoid 

 Terebratulids ; and when he gave it, also for long afterwards, all 

 such diphyoid Terebratulids were lumped under the name Tere- 

 bratula dvphya. As a name now seems necessary for an unoccupied 

 series of diphyoid Terebratuloids, and as there is this name in 

 print, it appears desirable to employ it. From the various diphyoid 

 Terebratuloids which it would have covered, one is now selected 

 to be the genotype, namely, Terebratula diphyoides, d'Orb. 



For forms in the bifidate stage, see d'Orbigny, pi. dix, figs. 3 & 4; 

 and Pictet, pi. xxiv, figs. 15 & 16 (see PI. XLI, fig. 18). Morphic 

 equivalent of A. dilatata is Pictet, pi. xxiv, fig. 11 ; of A. Catulli, 

 Pictet, pi. xxiv, fig. 13 ; of A. cor, Pictet, pi. xxiv, fig. 12 ; and of 

 A. angusta, Pictet, pi. xxiii, fig. 2 (see PI. XLI, figs. 20, 21). A 

 remarkably transverse form with very rounded angles is Pictet's 

 pi. xxiii, fig. 7. All these forms are named T. diphyoides, but 

 they represent various stages of phylogenetic development. The 

 size of the perforation, the plain, straight side-margin, and generally 

 the rounded-off angles distinguish these forms from their morphic 

 equivalents in Antinomia. The dorsal fold and the ventral sulcus 

 of the preperforate stage distinguish them from Pygope. 



Tor other figures of Pygites see Ooster [26], pi. v, figs. 1-3, 4 ? 



Pygites diphyoides (d'Orbigny). (PI. XLI, fig. 19.) 



Terebratula diphyoides, d'Orbigny, 1851, pi. dix, figs. 6-9 onlv. Id., Pictet, 

 1867, pi. xxiii, figs. 4, 5, 6, 8 ; & pi. xxiv, fig. 14. Id., Davidson, 1869. 



Remarks. — Davidson figures the loop of this species [14]. 



A series of Pygites spp. decreasing in size and angularity are shown 

 in PI. XLI, figs. 20-22. 



As a conclusion to these observations on the diphyoids I would 

 append a few remarks : — (1) Upon some Jurassic Terebratuloids 

 which show analogous stages of development; and (2) upon an 

 analogous case of successive independent development of like forms 

 among a certain group of Ammonites : the history of their nomen- 

 clature forms a most instructive parallel to the case of the 

 diphyoids. 



1 For subsequent quotation of MS. names, whether generic or trivial, I 

 suggest this practice — that the name of the giver of the MS. appellation be 

 hyphened to that of the describer, so as to give to the first his due — the latter 

 name indicates where the description may be found. Thus this name would 

 be subsequently quoted as ' Haan-Buckman.' 



