NATURAL SCIENCES OF PHILADELPHIA. 



291 



immediately in advance of the anus ; the same part in the female, 

 shows a conical flap depending from the front of the vulva. 



Having only about a dozen adult specimens of this species to 

 examine, the full range of variation can only be given with approxi- 

 mate accuracy. Still theseries is a very good one as far as it goes, 

 and the number of alcoholics afford reliable measurements. Dr. 

 Woodhouse's type is much faded by twenty 3'ears' exposure to 

 the light. The others agree perfectly in coloration, and the dif- 

 ferences in size are slight. I may here remark, that in the table 

 of measurements given by Prof. Baird, the dimension (nose to 

 tail) given from the dried specimens there enumerated is cer- 

 tainly over the mark. Thus, Woodhouse's type is given as 4.12 

 long, whereas the original description of the same specimen gives 

 this dimension as 3.50. 



Measurements. 



Taking the last seven sets of measurements of the fore^oingc 

 table (all made from sexed specimens in the flesh, and taken by 

 the same person, 2 so that a source of error which lies in different 



1 The measurements of length and of tail vertebrae are from Woodhouse. 

 In its present state the tail, as well as can be judged, is about 4.50 long, 

 exclusive of the terminal pencil, which is half an inch more. The dry mea- 

 surements are not reliable. 



2 In measuring tails, I take as nearly as possible the true length, by 

 placing one leg of the compasses snugly above the anus. The. length to 

 which the tail projects beyond the body-hairs, or its ostensible dimen- 

 sion, is considerably less. 



