MKl;i;iAM THK THAI.ATTdSAriil A 



21 



pelvis, and that the characters of either or l)oth of them are such as to show- 

 that the pelvis was not of the i>late-like form usually seen in the primitive 

 Diaptosauria. 



Both of the elements (lescril)e(l from the pelvic rei-ion of the type specimen 

 are large comi)are(l with the coi-aeoid, sea}iula and humerus. No matter how 

 we interpret them, they show that the posterior lind)s were possibly more 

 powerful than the anterior, reminding us of tlie peculiarly s[)eciali/,e(l Thalatto- 

 suehia of Frass. 



Pectoral Arch. — The ]>ectoral girdle is represented hy the eoracoid and 

 scapula. No clavicle or intertdavicle has as yet been discovered. Several 

 fragments of large l)ones associated with the jx'ctoral 

 girdle mav represent one or hotli of these elements. 

 The eoracoid (PI. viu, fig. 1) is reniforni and has some- 

 what the form of the eoracoid in the ichthyosaurian 

 genus Merria)ina from the same horizon. It is, how- 

 ever, more distinctly reniforni, having a sliarply conca\-e 

 exterior margin. 



The scapula (I'l. viii. Hgs. 2 and ;>) is comparatively 

 narrow reseml)ling that of the ( "roeodilians, Farasuchi- 

 ans, the later Ichthyosaurs, and most of the rhyncho- 

 cephalian forms. It differs from that of the Triassic 

 hdithvosaui's in lacking the considerahle distal expan- 

 sion. 



The structure of the pectoral arch, so fai' as 

 known, seems more primiti\'e than that of the Ti'iassic 

 Ichthvo.saurs and is of distinctiv rhvnehocephalian tvi)e. ^V^ '^^ Jl"^^''ttom,'ru. ale,- 



• ' . ^ 'I iiiulrne. A portion ol the n>:lit 



Anterior Limb. — Elements belonging to the anterior |„.,toial arch and limb seen 

 limbs are found in the type and in two other specimens. 

 In the tvt)e the humerus and tlu' ulna are present. In 

 another specimen both the humeri are widl preserved 

 and with them is, a nearly perfeet radius. 



The Jtiiinrrai^ (PI. vin, figs, 4" and 4/^ is consideralily expanded dorso- 

 vi'utrally at the proximal end through the dev<dopinent of a very heavy pectoral 

 ridge extending to the nuddleof the shaft. The distal en<l is greatly broadeiu'd, 

 its width equaling two ihii'ds tlu- length of the bone. In either inferior or 

 superior view the middle of the shaft appears more slender than is actually the 

 case, owing to the fact that the expanded ends are twisted at right angles to each 

 other. Poth the pi'oximal and distal ends seem to be deeply excavated, and 

 evidently supported large cartilaginous caps. In one specimen (PL viii. tig. Ah) 



1" 



from above, X %. f, eoracoid ; 

 N. scaimla; //. Inimerus; R, 

 radivis; V, uhia. 



