PROCEEDINGS OF THE NATION'AL MUSEUM. 61 



Type. — Mecistocephalus attenuatus (Say), 1819, the synonymy of which 

 is as follows : 



GeopliUus ferrugineus, C. L. Keen, Deutsclil. Crnst. Myr. u. Araoh.. 1835. 

 Paehjpnerlinnferritgineum (C. L. Koc'ii), System der Myriap., p. 187, 1847. 

 Mecistocejihalua fiilvus (Wood), Jouru. Acad. Nat. Sci. Pliila., V. p. 41, 1863. 



Distribution. — Europe, Korth Africa, Canary Islands, Eastern North 

 America. 



- This disposition leaves the species hitherto called Meci.stocephalus in 

 need of a generic name, and Dieellophllas is i)roposed for the sj^ecies 

 congeneric with Mecistocephalus Umatns, Wood, in allusion to the forked 

 chitinous thickening of the ventral plates. The species which this 

 change affects are: limata (Wood), hreviceps (Meinert), melanonotus 

 ( Wood) , quadrata ( Wood ). Tliis genus is further defined by the frontal 

 lamina being completely chitinized above the labrum, the margin of the 

 labrum laciniate, and the cephalic lamina without a claw-like chitinous 

 callosity at the sinus of the frontal lamina. 



The generic name Lamuonyx may be applied to the species which 

 have the cephalic lamina incompletely chitinized, the margin of the 

 labrum entire, and a claw at the anterior corners of the cephalic 

 lamina below. Lamnonyx leonensis^ I'lay be taken as the type. The 

 claw-like structure of the cephalic lamina seems not to have been 

 observed previously, but as I find it on all the specimens at hand from 

 the Eastern Continent, the species to be referred to Lamnonyx, pro- 

 visionally at least, are the following: carniolensis (C. L. Koch), casta- 

 we/cejM- (llaase), f/igas {ll'daae), japonicus (Meinert), leonensis, maxUlaris 

 (Gervais), punctifrons (Newport), punctilahrum (Newport), spissus 

 (Wood), tennicuJns (L. Koch), synonyms having been omitted. These 

 species are mostly in need of study which shall make known the 

 character of the mouth parts. 



Mecistocephalus microporiis, Haase, is apparently generically distinct 

 from the others by reason of tlie very numerous segments, the enor- 

 mous pleura', and peculiar conformation of the posterior scuta; it may 

 stand as the type of a new genus, to be called Megethmus. The genus 

 Bi cello phil us may be taken as the type of a distinct family, sei^ara- 

 ble from the Geophilida^ and Notiphilidai by many characters, among 

 which are the following: Body attenuate caudad; head large, long, 

 and narrow; frontal lamina always distinct, more or less chitinized 

 above the labrum. Cephalic lamina not concealing the prehensors; a 

 claw-like callosity at the sinus of the frontal lamina. Labrum entirely 

 free, tripartite, the median part very small, the lateral parts large, 

 transversely carinate. Lamin;!:' fulcientes linear, extending^ back past 

 the maxillary sternum as chitinous margins of the cephalic lamina. 

 Mandibles with numerous pectinate lamellic; no dentate lamelhe. 

 Labial sternum always divided, simple : labial pal])us and interior labial 

 process subsimilar in shajDC, distinct, consisting^ of a basal portion 



' A uew species from Sierra Leoue aud Liberia, in tlie National Museum collection. 



