108 BULLETIN 114, UNITED STATES NATIONAL MUSEUM. 



Comparison of the coast forms with respect to the shape of^^the 

 head and its scutes shows considerable divergence. Such compari- 

 son may be tabulated as follows: 



Character. 



boylii. 



getulus. 



Snout 



More blunt 



More pointed. 



Less than twice as wide as 



Rostral 



About twice as wide as high 

 (proportion of height to 

 width averages distinctly 

 less than in getulus). 



Usually longer than high 



Increased 



Loreal 



high. 



Usually higher than long, or 



as high as long. 

 Reduced. 



Internasal suture 



Eye 



Larger— its diameter gener- 

 ally greater than the great- 

 est height of the 4th upper 

 labial. 



Usually fails to reach the 

 posterior limit of the pari- 

 etal. 



Averao'e lower 



Smaller — its diameter gener- 



Upper temporal of third 

 row. 



Supralabials 



ally less than the greatest 

 height of the 4th upper 

 labial. 

 Usually extends to the pos- 

 terior limit of the parietal. 



Average deeper. 



About as long and nearly as 

 wide as anterior, and in 

 contact or separated by not 

 more than one small scale. 



Posterior chin shields. . . 



About half as wide and half 

 as high as anterior, and 

 separated by two smaller 

 scales. 



Briefly interpreted, getulus has a higher and more pointed head 

 to which the deeper loreal and supralabials contribute, and hoylii 

 has a lower, flatter, and blunter head. The shape of head in Jiol- 

 hrooTci is decidedly like getulus; yumensis and conjuncta are decidedly 

 like hoylii; it is in splendida that we find a mean between these ex- 

 tremes, and the closest similarity with the other groups of the genus, 

 and in the forms east and west that we find speciahzation. 



The penis is essentially the same throughout the group. In hol- 

 hrooki and niger, however, the basal half of the organ is beset with 

 minute spines. It would be easy to say that this condition is primi- 

 tive, and that the others have been derived by reduction of these 

 small spines. But primitive conditions generally show more per- 

 sistency than this. Most of the other structural characters show a 

 marked degree of permanence; reduction or increase is the excep- 

 tion, not the rule. In the calligaster group, the one nearest related 

 to this, the copulatory organ has the minute spines, when present 

 at all, usually restricted to the immediate vicinity of the large ones. 

 This is the situation that holds in the triangulum group and else- 

 where in the getulus group, except that there may be a slight ten- 

 dency toward extension of these spines in yumensis and hoylii. Thus 

 these small spines of the penis, instead of favoring holhrooTci or niger, 

 as ancestral, are distinctly against it, for the reason that they rep- 

 resent a speciaHzed condition not foimd elsewhere in the genus. 



In getulus, too, this organ is decidedly specialized. The bilobed 

 condition, noted in the descriptions for holhrooTci and probably for the 



