Pomona College Journal of Entomology 653 



scattered over the entire surface. Anal legs with six articles distad of the 

 coxopleurae. 



Mecistocephalus is the only North American genus of the family at present 

 known. 



Genus Mecistocephalus Newport 



In tliis genus tlie head is very large with tlic cephalic lamina much longer 

 than wide and uniformly narrowed from tlie front caudad. The antennae are 

 rather large and are a little attenuated from the proximal and distad. The labrum 

 has the middle piece very narrow and acutely jwinted distad while the side pieces 

 bear a fringe of very short pectinse. In the first maxillae the branches are 

 membranous distad. Anal legs without claws. 



So far as known the number of legs is invariable for each species. 



In California there are two species of this genus, M. limatus Wood and M. 

 anomalus Chamberlin, which are easily separated on the basis of the number of 

 pairs of legs, tlie former having forty-five and the latter forty-one pairs. 



Mecistocephalus limatus Wood 



This is one of the commonest members of the Geophiloidca in the central 

 portion of the state and also ranges to the southern portion, though it is not often 

 met with during the dry season. During the rainy months it often occurs in great 

 numbers under the fallen leaves of wooded areas. It seems to be especially 

 abundant about San Francisco Bay 



A large robust species often attaining a length of ()() mm. or more, while 

 the head as a whole may be 2..) to nearly 3 mm. across in large individuals. The 

 body is conspicuously attenuated from the head caudad. The head and body are 

 polished shining. Head and antennae dark reddish or chestnut in color; body and 

 legs orange or rustjf j'ellow, the dorsal scuta, especially on anterior portion of 

 body, often with a narrow dark band along caudal edges. Antennae long, atten- 

 uated distad. The claws of the prehensors when closed extend nearly to the 

 distal end of the first antennal article, each prehensor armed with four strongly 

 chitinized teeth, one on each article, of which those of the first article and claw 

 are largest. Anterior sterna with a deep longitudinal median sulcus which 

 becomes less strongly develojied caudad. First spiracle much larger than the 

 second, vertically elliptical, the others circular or nearly so. Last ventral plate 

 strongly narrowed caudad, triangular. Coxopleurae of last segment with numerous 

 small pores and usually one larger one distributed over most of the surface, the 

 number few in immature individuals. Pairs of legs in both sexes, so far as 

 observed invariably forty-five. 



Specimens have been examined from the following localities: Mill Valley, 

 Sausalito, Berkeley (author) ; Stanford (Mann) ; and Claremont (Pomona College 

 collection). 



Mecistocephalus anomalus Chamberlin 



This species in size, coloration and general structure is very close to the 

 preceding one. It is readily separated in having invariably forty-one pairs of 



