6 PROCEEDINGS OF THE ISTATIOlSrAL MUSEUM vol.73 



mainland of Nayarit. It was taken as late as 1913 at San Bias, 

 Nayarit, by J, C. Thompson. The species hrevirostris and pectinata 

 range from Nayarit southward to Oaxaca, in company with other 

 species of the genus, while parlceri, a new species, is described from 

 specimens from Barranca Iberra, Jalisco, However, its distribution 

 extends to Nayarit, specimens having been taken at Tres Marias by 

 M. Forrer about 1885. The species quinquecarinata is known only 

 from Tehuantepec, Oaxaca, while clarki has been collected at only 

 one known locality — Ovopeo, Michoacan. The form defensor is very 

 rare and has been taken only in Yucatan, but similis is very common 

 throughout southern Mexico and Central America, including Panama, 

 and is perhaps the most abundant species of the genus. 



Slight variations occur throughout the genus, not only in the species 

 but even in the individuals. It is not at all uncommon to find speci- 

 mens having a different number of femoral pores on the two legs. 

 The femoral pores are much larger in the males than in the females. 

 Glands at the base of these pores, in both sexes, produce a brown 

 waxy secretion which hardens and protrudes from the openings. 

 Although its function is unknown it appears to be most conspicuous 

 during the mating period, and it may have some significance in that 

 connection. Furthermore, the femoral pores are not always limited 

 to one row. Individuals have been examined in which the pores num- 

 bered 7 on each side, 5 in one row and 2 in a second row, parallel to the 

 first. Another specimen having 7 femoral pores on each side had 6 

 in one row and 1 in the second-row position. Both sides were patterned 

 alike. The number of spines or lobes making up the dorsal crest also 

 varies considerably with the species and sex. These dorsal crest spines 

 are larger in the males than in the females. Age also causes a differ- 

 ence in the size of the dorsal crest — the older specimens possessing 

 the tallest crest. 



Individuals have been examined in which the number of small flat 

 scales separating the whorls of large spinous scales on the upper half 

 of the tail dift'er on the right and left sides of the (fentral row of caudal 

 spines. Sometimes the first and second whorls are separated by two 

 rows of flat scales, the second and third whorls by two rows on the 

 right and three on the left; and occasionally one of the spinous whorls 

 is omitted on one side, giving that side twice as many, plus one or two 

 additional, flat scales. This arrangement of the scales does not appear 

 to be due to the loss of any, but merely to their disarrangement, for 

 in the succeeding rows the "omitted" scales are found crowded in; 

 thereby evening the count on both sides of the dorsal row. The 

 greatest variations are to be found in the coloration of the individuals. 

 This question is discussed under the respective species involved, 

 especially in liemiloplia and similis, so it is sufficient to say at this 

 point that the 5^oung and adults differ very greatly in coloration — 



