1888.] PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 383 



Dorsal spots divided longitudinally by a median black connection ; front 



black 0. d. gentilia. 



(3/3. Lateral borders of saddles not confluent with each other below. 



Saddles completed on gastrosteges ; no alternating spots ; no black col- 

 lar 0. d. parallel us. 



Saddles completed on gastrosteges ; spots opposite intervals forming a sin- 

 gle series on the middle line of the belly O.d. syspilus. 



Saddles completed above the gastrosteges ; alternating spots which do not 



meet on the middle line of the belly O.d. doliatus. 



II. A yellow band from orbit, bounded below by a black or brown one. (Saddle spots 



closed laterally above gastrosteges; superciliary light spots or bands.) 



A half collar touching occipital plates; no neck bauds; alternate spots largely on 



gastrosteges O.d. collarw. 



Neck with longitudinal bands ; alternate spots on gastrosteges O.d. clericus. 



Neck with bauds; alternate spots entirely on scales 0. d. triangulus. 



The more detailed transition from the simple head coloration of the 

 0. d. coccineus to the complex pattern of the 0. d. triangulum is accom- 

 plished as follows: 



A yellowish spot is seen on the superciliary plate of the siugle speci- 

 men of the 0. d. parallelus known, and on three of the fifteen speci- 

 mens of the 0. d. sysinlus. It appears in all of the thirteen O. d. 

 doliatus, and in two of these they nearly join across the front, and in 

 three they join, forming a cross-band. In four specimens of the 0. d. 

 doliatus a notch of the black anterior border of the nuchal collar appears 

 on each side. The deepening of this notch till it reaches the eye defines 

 the two postocular stripes of the subspecies of section u of the preced- 

 ing table. It has not quite reached the orbit in Nos. 7849 and 2192 of 

 0. d. collaris. The superciliary spots have not united across the front 

 in any of the five specimens of 0. d. collaris, excepting in .No. 5449. In 

 No. 2433 it is nearly completed. The interorbital and postorbital bands 

 are complete in the subspecies 0. d. clericus and O. d. triangulus. Fi- 

 nally, the completion of the head ornamentation is seen in the perfect 

 definition of the anterior boundary of the brown band in front of the 

 interorbital light baud. This is seen in three individuals of the 0. d. 

 clericus and in three of the five 0. d. triangulus. In one of the latter 

 it is simply indistinct; in another it is converted into a median spot by 

 a yellow band, which extends from the interorbital band round the 

 canthus rostralis and end of muzzle. 



This species furnishes, then, a most instructive illustration of the 

 origin of color character. 



The geographical distribution of the Ophibolus doliatus extends from 

 latitude 48° through the eastern Austroriparian and southern part of 

 the central district, and throughout Mexico and Central America to 

 Panama. It is wanting from the Pacific and from the Sonoran districts. 

 It does not appear on the west coast of Mexico north of Colima and 

 Michoacan. 



The phylogenetic relations of these subspecies may be sketched as 

 follows. Which is the ancestral form is uncertain; but as the region 



