398 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.53. 



Size. — Adult size is subject to some local variation, but is other- 

 wise constant. In the/wsca and ocTirophaea groups males are larger 

 than females. 



The disparity in size is greater than the total length measurement 

 would show, as the tails of females are larger than the tails of m.ales. 

 Similarly the much greater size of quadramaculata is better shown 

 when measurements of head and body are compared as the shortness 

 of the tail in this form obscures the difference when total lengths are 

 compared. 



Costal grooves. — The costal grooves are not of much use in separat- 

 ing forms of this genus. They vary from a minimum of 12 in quadra- 

 maculata to a maximum of a possible 15 in hrirrdeyorum. Fourteen 

 is normal, counting the axillary and inguinal. The inguinal in 

 specimens with 14 may be either a distinct groove or a fork of the 

 thirteenth. Where there are only 12 this fork is lacking and No. 1 

 does not quite reach into the axilla. To quote from Cope (1889) 

 speaking of ochropJiaea: "The costal folds are 13, but 14 if that which 

 is immediately above the groin be counted. The first falls un- 

 mediately into the axilla. This is the characteristic arrangement in 

 D. fusca also, while in D. nigra the fold above the groin usually 

 extends to it and is the twelfth, while that which corresponds to the 

 first of the species last named falls just in advance of the axilla. 

 Though this is typical of D. nigra, occasionally another plica appears 

 above the groin and the twelfth is slightly in front of it." 



It will bo seen from this that the number of costal grooves in this 

 genus can not be used as a character of any great value. 



The tubercle canthus oculi is present in aU forms save typical 

 ochro'phaea. I have been unable to use the lateral pores as diagnostic 

 characters. This is largely because the distinctness of these pores is 

 so dependent on the preservation. In some specimens they are 

 quite evident. In others of the same species they are scarcely to be 

 observed at all. 



Color. — The shades are extremely variable, but I have found the 

 general markings to be quite constant. In all of the forms there is a 

 marked tendency for the dorsal surface to become black with age. 



In quadramaculata the ventral surface also becomes dark with 

 age, and caroUnensis aad monticola show a tendency in this direction. 

 In the other species the beUy assumes its permanent coloration 

 shortly after transformation. 



Measurements. — In measurements the head length is taken from 

 the tip of the snout to the middle of the gular fold. The head width 

 is taken at the angle of the jaws. The tail is taken as beginning at 

 the posterior angle of the vent. 



