COUES AND YAKROW ON HERPETOLOGY. 273 



just named being new. To these several more have since been added, 

 chiefly by Mr. Kennicott and Professor Cope, from various parts of the 

 West, the present number of current United States species being over 

 twenty. 



That the species of this large and difficult genus require thorough 

 critical revision, with a reduction of the number of accredited species, 

 will be evident to any one who undertakes the identification of any con- 

 siderable series of specimens. A certain proportion of the specimens 

 cannot be referred without hesitation to the described species they are 

 supposed to repi^esent, or, rather, may be referred, with about equal 

 propriety, to more than one such species. This indicates either that the 

 descriptions drawn from particular type-specimens are too exclusive to 

 fairly afford specific diagnoses, or that the supposed species they repre- 

 sent are not valid, but blend with each other through intermediate spe- 

 cimens. There is unquestionably a gentle and complete intergradation 

 between several of the accredited species. 



Too much stress altogether has been laid, in the preparation of spe- 

 cific diagnoses, upon points which should properly be only adduced in 

 illustration of the normal inherent range of variation of the individual, 

 and have no value whatever as functions of the actual specific equation. 

 For instance, " superior labials seven" and "superior labials eight" are 

 expressions found in the diagnosis of certain species as distinguishing 

 marks. Whereas the fact is, as any one may satisfy himself by exam- 

 ination of the first dozen specimens of Uutcenia that come to hand, that 

 the superior labials may be either seven or eight in different spe- 

 cimens of indubitably the same species, or that there may be eight of 

 them on one side of the mouth, and seven on the other, in the same 

 specimen. Subdivisions of the genus have been based upon the number 

 of dorsal rows, whether 17, 19, or 21. Whereas it is a fact that different 

 specimens vary a pair or two of scales in this respect, and that different 

 parts of the body of the same specimen show a different number of rows 

 of scales. Other matters, such as the width and sharpness of definition 

 of the characteristic stripes, and the special tinge of coloration of these 

 and other parts of the body, might be mentioned in similar terms. 



As far as we have seen, the position of the lateral stripe may be a 

 means of grouping the species. Though this varies within certain limits, 

 mainly according to the width of the baud, yet its position on the third 

 and fourth, or on the second and third, dorsal rows, affords a ready 

 means of distinguishing certain sets of species or varieties. 



Along the northern boundary, Eutcenia is the best represented genus 

 of Ophidia, and indeed of Beptilia^ not only in numbers of individuals, 

 but of species as well. They occur in all situations, excepting, as a 

 rule, the most arid regions, and are particularly numerous about the 

 prairie pools and sloughs and along the banks of the various streams. 

 All the species represented are more or less aquatic, particularly during 

 Bull. iv. No. 1—18 



