40 CRETACEOUS GASTROPODA 
figs. 6—8. All the specimens are imperfect with regard to the aperture, but the 
outer lip could not have been very much expanded. The shell, as it appears from 
single fragments, has been smooth similar to other Pterodonte and Rostellarie. 
The number of species of Pterodonta, which, as at present defined, has been 
found chiefly in cretaceous deposits,* is tolerably large. This might be to some 
extent expected from the well-known great representation of the family Azara in 
cretaceous rocks. In addition to the five species already mentioned, the following 
are quoted by Pictet under the genera Péerodonta and Tylostoma (vide Mat. Pal. 
Suisse. 3me Ser. p. 676 and pp. 858—359). Pterodonta elongata, inflata, naticoides, 
ovata, intermedia, pupoides and scalaris, of D’Orbigny ; Pterodonta obesa, Coquand ; 
Pterodonta (Tylostoma or? Varigera) Ricordeana, Rochatiana, Fittoni (rather 
Fittoniana, from the Isle of Wight), Hscragnollensis, Guerangeri (Guerangeriana), 
Carentonensis and Toucasiana of D’Orbigny ; Pterodonta Torrubie, punctata, ovata 
(this must receive another name) and globosa of Sharpe; Pt. Laharpi (Laharpiana, ) 
fallax, Villersensis, naticoides (must receive a new name), elliptica, depressa and 
geultina,t of Pictet and Campiche. Péer. subinflata, Coquand, (Geol. and Pal. 
de Const. 1862, p. 179) has been proposed for the Algerian species, which was 
first noted by Bayle as Pt. inflata, D’Orb. The Natica patens, Binkhorst 
(Mon. Gast. et Ceph. craie sup. de Limbourg. 1861, p. 18, Pl. II, Fig. 1) may 
very probably be shown to be a Pterodonta; certainly it is a strange Natica 
with “labro dilatato, reflexo.” Morris in his Catalogue (p. 274) quotes a species 
of Pterodonta, allied to Pt. elongata, D’Orb., from the upp. Greensand of 
Warminster, and a species of Zylostoma (ibid. p. 285) from the lower chalk of 
Chardstock. Morris follows D’Orbigny’s original proposition, as regards the former 
genus, but he places the latter in the Marrcrpz LThave to add here the Péero- 
donta crassa, Schafheeutl, (Siid-bayerns Leth. geognost}. Leipzig 1868, p. 193, 
Pl. LI, Fig. 1, named here by mistake Plewrodonta crassa). It is a species some- 
what like D’Orbigny’s P?. ovata in form, but neither in the description nor in the 
figures are any of the impressions noticed. Still it seems to be a true Pterodonta, 
and the omission of these impressions is probably due to the bad preservation of 
the specimen. It is impossible to say from Shafhzeutl’s singular references, whether 
the species is cretaceous or not, for he confounded every thing. 
* The two Jurassic species, which probably belong to Pterodonta, are Melania gigas, Thurmann, (Leth. 
Bruntrutana, p. 84, Pl. VI. Fig. 18) and Pterodonta corallina, ibid. p. 84. Ido not know where the second 
species is described. 
+ It would be premature to change this and other specific names, because the other Pf. gaultina 
(Aporrhais, Pictet,) could be placed in another genus or subgenus, or whatever it may be called. 
~ I may be excused, when in the following pages I have occasionally omitted a reference to this publica- 
tion of Mr. Schafheutl. Iam compelled to do so, because it is impossible for me to make out, which fossils are 
cretaceous and which are not, and to refer to the former only can be my present object. There is in reality no 
very great loss, for most of the specimens are badly preserved casts, although occasionally described with 
the opereula! I should not like to pronounce an opinion on the merit of the geognostical studies, but it is 
to be regretted, that the valuable results, which could have been obtained from a careful examination of that 
interesting collection of fossils, have been made so thoroughly unavailable by the singular ideas regarding 
geognostical formations. 
