478 MR. G. A. BOULEXGER ON THE [Apr. 19, 



ground of the articulation of the skull with the atlas by a pair 

 of cotyles in the basioccipital bone, coi-i-esponding in position with 

 the Mammalian occipital condyles, whilst the median part of the 

 bone, which forms the floor of the foramen magnum, is produced 

 in the position occixpied by the median occipital condyle of 

 Reptiles. Cope alludes at the same time to an '' enormous fronto- 

 pai-ietal foramen." 



In Cope's classification of 1889* the Cotylosauria are defined 

 as Theromora with the coi-acoid i-educed, not meeting the 

 sternum, the ribs single-headed, the temporal fossa " overi-oofed," 

 the dentition " abundant," and intercentiu present. The Pario- 

 sauridpe are included in addition to the Diadectidse ; and in his last 

 contribution, " The Reptilian Order Cotylosauria," t the Elginida^ 

 and Pai'iotichidee t are also added, the former of which appeal-, 

 from our pi-esent, imperfect knowledge, to be close allies of the 

 Pariosaui'ida?, without any special affinity to the Diadectidse. 



The restoi-ation of the very imperfect uppei' part of the skvill 

 of Diadectes and allies, as originally given by Cope §, is not to be 

 relied upon, since the illvistrious American palaeontologist, in his 

 later writings, defined the Cotylosauria as with the temporal 

 region entirely i-oofed over by bone. That a small supi-atemporal 

 fossa might have existed appeai-s from the following bi-ief state- 

 ment recently made by Case |j : — "It is of interest to note that 

 the author discovered perforations in the roof of the skull of the 

 Diadectidte in the Cope Collection in the position of the superior 

 temporal vacuities ; the foi'ms are too specialised to make the 

 interpi'etation of this occurrence cei-tain, but it may well be the 

 first step towards the Proganosaurian type." Di-. Case, has how- 

 evei', since written to me (Dec. 12, 1903) that these vacuities do 

 not occur in a second specimen from the same region in the Cope 

 Collection. He kindly adds : — " The skull of the Diadectids is 

 very rugose and the sutures ai-e very obscui-e ; thei'e ar-e certainly 

 no distinct tempoi'al arches and the position and limits of the 

 bones of the temporal region is uncertain. The whole region was 

 covered by a complete i-oof in all the specimens but the one 

 noticed, and the quadrate is closely connected with the i-oof -bones, 

 so that the whole region has a strong supei'ficial resemblance to 

 the turtles." Dr. Case has ascertained, moreover ^, that the 

 pectoi-al arch of the Diadectidse consists of scapula, coi-acoid, pi-e- 

 coracoid, clavicle, and interclavicle. Cope ** has given a very 

 brief description of a Diadectid pelvis, which agrees in all 

 essential chai-actei's with that of Frocolophon and Telerpeton. 



* Amer. Natur. xiv. p. 304. In this classitication, the FrocolophoHida arc phict'd 

 ill the incongi'uous assemblage Proganosaiiria. 



t Op. cit. xxiii. p. 866. 



t E. T. Newton, Phil. Trans, clxxxiv. B, 1893, p. 473 ; E. C. Case, Zool. Bull, 

 ii. 1899, p. 231. 



§ Proc. Amer. Philos. Soc. xix. 1880, pi. v. 



II Amer. Natur. 1903, p. 99, footnote. 



1" Amer. Journ. Geol. xi. 1903, pp. 397 & 400. 



** Proc. Amer. Philos. Soc. xx. 1882, p. 448. 



