THE MICROSAURIAN FAMILY AMPHIBAMID^. 



129 



The osseous part of the vertebra seems to have been but a thin shell, and the struc- 

 ture of the zygapophyses can not be determined. That they were dorsal in position 

 is, however, evident from several vertebrag. The points of these structures project 

 laterally. The tail is short and the caudal vertebras weakly developed. 



There are distinct impressions of at least 12 pairs of ribs in the Daniels specimen. 

 They are long, slender, and curved, and there is no definite assurance that there were 

 as many ribs as are indicated (fig. 26) in the restoration (462). The ribs are inter- 

 central (469) and probably occu- 

 pied the full length of the verte- '°''^- -'»' 

 bral column. There may have 

 been as many as indicated in the 

 restoration. 



One of the most interesting 

 features of the Yale specimen is 

 the preservation of a small patch 

 of skin, evidently from the back, 

 lying to one side near the head, 

 measuring 5 mm. in length by 3 

 mm. in width. The fragment 

 shows the skin to be of tubercu- 

 lated scales, 4 of which occupy 

 the length of i mm. The scales 

 are somewhat hexagonal, almost 

 rounded, and were relatively 

 quite thick. They lie in a close 

 mosaic (fig. 27). 



The Yale specimen has, very 

 well preserved, a portion of the 

 ventral scutellae, of the throat, 

 chest, and belly. The arrange- 

 ment of the plates on the throat 

 and chest is almost exactly the reverse of what Credner has described (190) for Bran- 

 chiosaurus amblystomus Cred. On the throat, in the present form, the chevron points 

 anteriorly, and it is the anterior prolongation of the belly scutes with the postero- 

 lateral projection of the gular scutes which form the chest and arm scutellation. The 

 belly chevrons point anteriorly, as in Branchiosaurus, the rods formed by the scutes 

 being straight and not curved as in Branchiosaurus. The entire ventral armature pre- 

 served is displaced to the left of the animal and only the anterior portion is preserved. 



The pectoral girdle is only partially known. The scapula is crescent-shaped. 

 The other elements are indicated only by fragments and nothing is known of 

 their form. 



The arm elements are nearly all known. The humerus is slender and expanded 

 at the ends, with its articular surfaces well developed. The separate radius and ulna 

 are of approximately the same size and length. The carpus is unossified. The com- 



FiG. 27. — Skeleton oi Amphibamus grandiceps Cope. X i-4. 



carpus; cl, clavicle; cr, caudal rib; cii, caudal vertebra; /, femur; 

 h, humerus; il, ilium; s, skin; or, orbit; r, radius; «, ulna; sc, 

 scapula; sp, sclerotic plates; t, tibia and fibula; ts, tarsus; vs, 

 ventral scutellas. Specimen No. 794, Yale University Museum. 



