MYRIAPODA 53 



tinuous because the segments fit into each other with unusual compact- 

 ness. They are also readily separable from the Chelodesmidae, the 

 only West American group with which they could be confused, by the 

 presence of a sharp spine on the lower distal corner of the second 

 joint of the legs. 



Xystocheir gen. nov. 



Type. Xystocheir obtusa sp. nov. from California. 



The distinctness of this genus from the East American Fontaria 

 is obvious from the totally different structure of the gonapod, which, 

 instead of a single or a double prong arising from a broad base, is long 

 and subconic, and ends in five spines, as described by Wood and shown 

 in the accompanying figures. In addition there are several secondary 

 sexual characters. The coxa of the third leg bears a large upright 

 process ; the coxa of the fourth leg has a broadly conic process on the 

 mesial face at base, and there is a pair of more sharply pointed proc- 

 esses arising from the sternum between the same pair of legs. Smaller 

 conic processes are also to be found on the sterna of segments 6, 8 and 

 9. All the legs of the male are crassate, and especially the second 

 joint, the lateral face of which is strongly inflated into a large hemi- 

 spherical prominence. The claws are long and are distinctly recurved 

 beyond the middle. 



XYSTOCHEIR OBTUSA sp. nov. 

 (pi. in, figs. ia-ic.) 



Type. No. 795, U. S. Nat. Mus. Collected in California by Capt. 

 Thomas L. Casey. 



Length of male about 28 mm. ; width 5.5 mm. ; length of antenna 

 about 5.5 mm., of leg about 5 mm. 



Color in alcohol fading to olive and olive-buff. 



Segments with posterior corners but slightly produced, the porifer- 

 ous callus small. Penultimate segment short, the angles of the cari- 

 na? not exceeding those of segment 18. 



Gonapods with second joint subconic ; lateral spine slender, nearly 

 terete, inserted at nearly the same level as the anterior, its apex pro- 

 jecting distad to opposite the bases of the distal spines. Posterior dis- 

 tal spine narrow, flattened, turned inward and forward ; anterior dis- 

 tal spine narrowly and sharply conic, the apex turned slightly forward. 



A single male specimen without detailed locality. The small size 

 and blunt carinae distinguish this species from the next. The gona- 



