Cope.] 452 LSept. 15, 



foramen chordie dorsalis, coossified with the neural arch, and supporting 

 transverse processes. Two rib articuhttions, one below the other, gen- 

 erally both at the extremities of processes, but the inferior sometimes 

 sessile. No neural spine nor diapophysis ; the zygapophysis normal and 

 well developed." 



This diagnosis was derived from the vertebrte of a single species from 

 the Clepsydrops shale of Illinois, the D. salamandroides, and since that 

 description was written, no additional specimens have come under my ob- 

 servation. In the Catalogue of the Vertebrata of the Permian I placed the 

 genus as the type of a family, the DlplocauUdce, among the Pelycosauria. 

 I am now, however, through the energy of Mr. W. F. Cummins, in pos- 

 session of specimens of a number of individuals of a second species of 

 Diplocaulus, found by him in the Permian beds of Texas. From them I 

 derive that the genus and family must be referred to the Stegocephalous 

 Batrachia. It is, however, exceptional among these in the fauna of which 

 it is a member, in not belonging either to the Rhachitomi* or to the Em- 

 bolomera, since the vertebral centra are not segmented, nor are the inter- 

 centra present in any form. Under these definitions it must be referred to 

 tlie suborder which includes Oestocephalus, Oeraterpeton, etc., for which I 

 have adopted Dawson's name Microsauria. The division includes genera 

 'witli simple amphicoelous vertebral centra, and teeth without inflections 

 of the dentine. The following characters must be added to Diplocaulus : 



Vertebraj with a more or less perfect zygosphen articulation ; centra 

 shorter in the anterior than in the median part of the column ; axis and 

 atlas solidly united by a long zygosphen, which is not roofed over by the 

 zygantrum. Neural arch continued as a short tube into the foramen 

 magnum. Atlas unsegmented, and, like the axis, without freehypapophy- 

 sis. Cervical vertebrae not distinguished from dorsals, and with two- 

 headed ribs. 



Orbit separated from the maxillary bone by the union of the lachrymal 

 and malar. Either the malar, or more probably the quadratojugal, extends 

 much posterior to the quadrate bone. It is bounded above by the squa- 

 mosal, Avhich extends anteriorly to the distinct postfrontal, thus covering 

 over the temporal fossa. Posteriorly it extends into a long, free process, 

 like the operculum of Polyodon ossified. This horn does not appear to 

 consist of the epiotic as appears to be the case in Geraterpteon. The 

 quadrate bone is extended very obliquely forwards and its extremity is 

 divided into an hourglass-shaped condyle. In other words the condyle 

 consists of two cones with apices continuous. The internal cone is the 

 smaller, and its base is overlapped from before by a flat bone, probably the 

 pterygoid. The cotyli of the mandible correspond. Mandible without 

 angle ; symphysis short. 



The teetli are of about equal size, and are rather slender and with conical 

 apex. Their surface is not inflected at any point. The superior series is 



* American Naturalist, 1882, p. 334. 



