THE MICROSAURIAN FAMILY SAUROPLEURID^. 1 65 



posteriorly. The element is nearly as wide as long. There is a prominent longi- 

 tudinal keel on the ventral surface of the interclavicle and radiating lines which 

 may indicate the courses of blood-vessels or nerves or may be the ornamentations 

 of the element, probably the latter. The clavicle has the usual microsaurian form. 

 It has three points and is truncate exteriorly. It is ornamented with radiating 

 grooves of a shallow and not strongly pronounced character. There is no evidence 

 of the coarse sculpture of the later forms. If the scapula is represented it is merely 

 by an indeterminate fragment insufficient for description. 



The pectoral limbs are preserved nearly entire. The left fore limb lacks only a 

 few phalangeal bones, and these were preserved with the remainder of the skeleton 

 but were lost in the mining process. The humerus is an extraordinary element on 

 account of its robust dimensions. It is very stoutly built and represents a power- 

 ful limb. It is expanded at each extremity and the width of its shaft is about equal 

 to one-fourth of its length. The ulna and radius present the same characters as 

 the humerus, i.e., in being robust, with stout shaft and expanded ends. The ulna is 

 slightly longer than the radius and has an expanded upper end. The radius is short 

 and does not have the proximal expansion. The carpus was cartilaginous. Its posi- 

 tion is represented by a blank space on the coal. There are 4 digits preserved and 

 in all probability this was the entire number. The metacarpals are elongate and 

 expanded at the extremities. The first and second digits are represented nearly com- 

 plete. The first digit is extremely interesting in the possession of a claw-like terminal 

 phalanx which much resembles that of some lizards. There are 3 phalanges in the 

 first digit and 4 in the second. The phalangeal formula may have been 3-4-4?. 



The ventral scutellation of this species is of an unusual character. It consists 

 of broad, imbricated scutes which are in a single piece and which are arranged in 

 the usual chevron pattern. The scutes were, apparently, broadest in the middle 

 and tapered somewhat at the extremities. This character alone is sufficient for 

 separating the genus from that of any other known form. 



The genus finds its nearest allies in the forms of the species of the genus Sauro- 

 pleura, in which Cope formerly located the present species. The skull of the form 

 described as Tuditanus radiatus Cope is quite similar to the present form, both in 

 the sculpturing and arrangement of the elements. The characters wherein the pres- 

 ent form resembles the species of Sauropleura are the possession of broad pectoral 

 plates and strong, digitate limbs. The general form of the body and skull is different 

 in the two groups. It is slender in Sauropleura and decidedly stout, short, and 

 heavy in Sanrerpeton. 



Measurements of the Type. 



mm. mm. 



Length of specimen 130 Width of clavicle 18 



Median length of skull 51 Length of abdominal scutes 28 



Width of skull at posterior border 62 Length of humerus ig 



Width of skull across orbits 48 Width of humerus at upper end 6.5 



Length of orbit 14 Length of ulna 1 1 



Width of orbit 10 Length of radius 9 



Interorbital space '16 Length of metacarpal 3 



Length of longest tooth preserved 4 Length of first digit 12 



Length of shortest tooth preserved i Length of terminal phalanx 3.5 



Length of the interclavicle 26 I..ength of lower jaw on the curve 70 



Width of interclavicle, maximum 23 Width of lower jaw, maximum 8 



I-ength of clavicle 22 Length of rib 30 



