Louis Dollo—On the Humerus of Euclastes. 261 
V.—On tHe Humerus or HuctrasTes. 
By Louis Dotto, C.E.; 
Assistant Naturalist in the Royal Museum of Natural History of Belgium, Brussels. 
I.—To avoid useless repetitions, I shall consider as admitted what 
I have said in my paper “ Sur le genre Euclastes,”’! especially : 
1. Huclastes, Cope = Chelone, Owen (non Ritg.) (pars) = Lytoloma, 
Cope = Puppigerus, Cope (pars) = Glossochelys, Seeley = Pachy- 
rhynchus, Dollo = Erquelinnesia, Dollo. 
2. The diagnosis of the Propleuride, as 1 have completed it. 
II.—This being stated, I think that the far more chelydroid than 
chelonoid humerus of the above-named Turtles is one of the most 
interesting facts of their organization. Indeed, if we remove, 
for the present, from the Dactyloplastrine Cryptodiran Thecophorian 
Chelonians : ? 
1. The Trionychide, with which the Propleuride have nothing in 
common, as is sufficiently proved particularly by their carapace and 
their plastron ; 
2. The Propleuride themselves, since it is precisely these which 
we are comparing with the others; we have only really to examine 
the two following types: 
1. The Chelonide ; 
2. The Chelydridea. 
Now, by their skull® and their proccelous caudal vertebre,‘ the 
Propleuride are related to the first-named family. Their carapace 
and their plastron would, it is true, appear to place them nearly at 
an equal distance between the Ohelonide and the Chelydride, especially 
on account of the degree of ossification. Nevertheless, as the nuchal 
bone does not possess the characteristic costiform process of the 
latter,> I think that we should not be justified in regarding the 
structure of the carapace and plastron as a sign of relationship with 
the last-mentioned family ; it is a question, in the case which we are 
considering, of a simple coincidence in two parallel series. The 
Propleuride might then be looked upon as aberrant Chelonide, ranking 
1 L. Dollo, ‘‘ Sur le genre Euclastes,’’ Société géologique du Nord, Annales xy. 
1887-88 (in the press). 
* L. Dollo, “ Premiére Note sur les Chéloniens du Bruxellien (Eocéne moyen) de 
la Belgique,’ Bull. Mus. Roy. Hist. Nat. Belg., t. iv. 1886, p. 84. 
3 R. Owen and T. Bell, ‘‘ Monograph on the Fossil Reptilia of the London Clay,” 
part i. Chelonia, Paleontographical Society, 1849, pp. 9 and 10; E. D. Cope, 
“* Synopsis of the Extinct Batrachia, Reptilia and Aves of North America,” Trans. 
Amer. Phil. Soc. Philadelphia, 1871, vol. xiv. p. 148; L. Riitimeyer, ‘‘ Ueber den 
Bau von Schale und Schadel bei lebenden und fossilen Schildkréten als Beitrag zu 
einer palaontologischen Geschichte dieser Thiergruppe,’’ Verhandl. d. naturforsch. 
Gesellschaft in Basel, vol. vi. 1874-78, p. 122. 
4 L. Dollo, ‘* Hueclastes,” etc. (Joc. cit.). It is known that, in the Chelydride, the 
caudal vertebree are opisthoccelous (E. D. Cope, ‘‘ The Vertebrata of the Tertiary 
Formations of the West,’’ Rep. U.S. Geol. Surv. Territ. (F. V. Hayden), 1884, p. 111). 
° G. Baur, ‘* Osteologische Notizen iiber Reptilien,” Zoologischer Anzeiger, 22 
Novembre, 1886, p. 688; R. Lydekker and G. A. Boulenger, ‘‘ Notes on Chelonia 
from the Purbeck, Wealden, and London Clay,’’ GrotocicaL Macazinz, June, 
1887, p. 273; L. Dollo, ‘‘ Premiére Note sur les Chéloniens oligocénes et néogénes 
de la Belgique,’’ Bull. Mus. Roy. Hist. Nat. Belg. t. v. 1888, p. 92. 
