MARYLAND GEOLOGICAL SURVEY 21 



Length lumbar (epiphysis hypo- 

 thetical) 3 in. 6.3 lines (87.6 mm.) 



Depth 2 in. 3 lines (54 mm.) 



Width 2 in. 3 lines (56 mm.) 



Width neural canal 3 in. 8 lines (66 mm.) 



Length caudal (one epiphysis 



supplied) 3 in. 10.5 lines (96 mm.) 



Depth caudal 3 in. 4 lines (58 mm.) 



Distance between inferior keels.. 10.5 lines (31 mm.) 



Width basis diapophysis 10.5 lines (31 mm.)" 



In 1869 the characters here given were corrected. "It was stated 

 to differ from Priscodelphinus in that, while some caudals had spinous 

 diapophyses, others possessed them flat, but imperforate. A vertebra 

 supposed to indicate the latter characters I am now compelled to refer 

 to another species and probably genus. Other vertebra assigned to 

 Z. flagellator must be referred elsewhere. A lumbar vertebra repre- 

 sents another species of probably the same genus, while a third has 

 evidently pertained to still a third species. The genus will be charac- 

 terized by the extraordinary length and slenderness of the lumbar 

 vertelirae, and similar, though slightly abbreviated form of the caudals. 

 The latter have spinous diapophyses, and in one species the former also. 

 While the width of the articular faces of the centra of these vertebrae 

 in the typical Priscodelphmus is but few lines less than the length, in 

 the species of this genus the diameter of the same is only from four- 

 sevenths to one-half of the length. The nearest approach is made by 

 Priscodelphinus stenus, where this diameter is six-sevenths of the 

 length." 



In the same article as the last quoted Cope gave a synopsis of the 

 characters of the species of this genus. 



" I. Median or anterior caudal with a strong* longitudinal keel above the 

 diapophysis — which is therefore probably present on the distal 

 lumbars. 



Epiphysis thicker, larger Z. flagellator. 



II. No longitudinal keel on lumbars, Diapophyses broad, flat; epiphyses 



thin, large Z. tysonii. 



III. Diapophyses narrow^, subspinoiis; epiphyses thin, small Z. velox." 



