470 rnocEEMNas or the national museum, vol. 40. 



A NEW SPECIES OF PERIDONTODESMUS FROM GUATEMALA. 



The small size of the first segment is the most striking external 

 feature that differentiates Peridontodesmus from Cryptodesmus. Po- 

 cock considers this as a primitive character in justifying the erection 

 of a family, but it seems more reasonable to look upon the peculiari- 

 ties of this segment as specializations in both cases. 



PERIDONTODESMUS PURULICUS, new species. 



Another species of Peridontodesmus, not studied by Pocock, has 

 the first segment less reduced, scarcely narrower than the rounded 

 anterior corners of the second segment, and with the lateral corners 

 less pointed than in the species studied by Pocock, though more 

 specialized in other ways. The teeth that border the anterior margin 

 of the first segment are of different sizes, five or six near the lateral 

 corners being much larger than those farther toward the middle. 



The antennae are distinctly clavate, but not geniculate; joints 1-5 

 short and robust, increasing in length and diameter; joint 6 about 

 twice as long as joint 5, more than twice as long as joint 7; joint 3 

 scarcely longer than joints 2 and 4 instead of much longer, as in 

 P. fiagellifer. These proportions are also widely different from those 

 found in Scytonotus where joint 3 is the longest, and joints 4 and 5 

 are nearly as long as joint 6. 



The dorsal tubercles are reduced so that the segments are nearly 

 smooth, though beset with three transverse rows of long hairs. Porif- 

 erous segments have the carinae dark brown like the middle of the 

 body, while segments without pores have yellowish carinas. 



The gonopods end hi three prongs, somewhat as in P. JiageTlifer, 

 with the short inner prong sharply decurved, as in that species, but 

 not so much exceeded by the relatively short and straight outer 

 prong. Middle prong expanded into a short, incurved plate, trun- 

 cate-emarginate at apex, and with the corners produced into small 

 teeth. The long retrorse basal prong of P. flagettifer is replaced by 

 a large rounded ventral prominence with a pencil of compact bristles 

 on its distal slope. Female genitalia broadly clavate globose, the 

 apical surface with a deep transverse groove. 



This species may be called Peridontodesmus purulicus. The type 

 is deposited in the U. S. National Museum (Cat. No. 809), a male 

 specimen collected at Purula, Baja Verapaz, Guatemala, by O. F. 

 Cook in June, 1904, measuring 8 mm. by nearly 2 mm. 



The bearing of these new forms upon the classification of Ohatelainea 

 lies in the fact that their characters connect Cryptodesmus with the 

 American series represented by Peridontodesmus and Scytonotus, and 

 perhaps even with the true Polydesmidae, rather than with the African 

 and other tropical types which it has been customary to refer to the 

 genus Cryptodesmus or to the family Cryptodesmida?. 



