ART. 25 CHINESE AMPHIBIANS AND REPTILES STEJNEGER 43 



by the contrast of the characters in combination, but that is of but 

 scant help in determining their relation to, or identity with, other 

 named forms known only from descriptions. 



The recognition of the various forms of Phrynocephalus belong- 

 ing to the Ph. caudwolvulus group is exceedingly difficult from de- 

 scriptions, no matter how accurate these are, and especially perhaps 

 when they are so elaborate and detailed as Bedriaga's. I am not 

 questioning the validity of the various forms described, but without 

 authentically identified material from type localities for compari- 

 son one can hardly ever be sure of the identifications. The trouble 

 is not only that these lizards are subject to endless individual varia- 

 tion, but the nature of their lepidosis is such that it leaves very few 

 definite points for measurements, so that some of the proportions to 

 which the describers have had to resort for key characters are so 

 vague that they give different results every time they are applied. 

 Thus the distance from tip of snout to preocular fold is so elusive 

 that it is hopeless to use it in connection with the internarial dis- 

 tance which has to be expressed in fractions of a millimeter. The 

 "height" of the head is another uncertain character, and the dis- 

 tance from tip of snout to gular fold. The figures can not by any 

 possibility be exact enough to be applicable to material of different 

 provenience and preservation. And so with most of the characters 

 employed, such as the carination, sharp or slight, and smoothness 

 of the dorsal scales, the homogeneousness or heterogfeneousness 

 of the dorsal lepidosis, etc. 



A careful and, let me add, laborious study of Bedriga's mono- 

 graph has convinced me that the series (U. S. Nat, Mus. Nos. 

 39319-25) of Phrynosomas collected by Sowerby on November 9, 

 1908, at Yulinfu, altitude 4,000 feet, are not true Ph. frontalis^ but 

 Ph. fotanmi. Bedriaga's series of nine specimens, collected by 

 Potanin at two localities in Ordos, from which Yulin is not very 

 distant, shows a great deal of variation, the description of which 

 covers the variations shown by Sowerby's series of seven speci- 

 mens, so that I shall not add to the accumulation of details already 

 on record. This species differs from true Ph. frontalis chiefly in 

 the lower head, wider internarial space, smaller dorsal scales, and, 

 as said before, with specimens of both species before one there is 

 no difficulty in distinguishing them. 



Mr. Sowerby has given a very interesting account of this species 

 in life, from which I quote, as follows : 



I have not met this little lizard anywhere but in, and on the border of, the 

 Ordos Desert. Here it may be seen in great numbers during the warmer 

 months of the year. These little creatures are very pugnacious, and indulge 

 in desperate battles with one another. They have a peculiar habit of rapidly 



