AET. 18 ISTEW GENEEA OF MILLIPEDS COOK AND LOOMIS 7 



Family SIPHONOPHORIDAE 



The genus Siphonophora has been the only representative of this 

 family in America. There are numerous tropical species, but until 

 recently no member of this family has been reported in or near the 

 United States. In 1923 a representative of the family was described 

 from Sonora, Mexico, and in the autumn of 1924 another was dis- 

 covered in the mountains bordering the northern edge of the southern 

 Arizona desert. This Arizona species offers sufficiently distinctive 

 characters to call for a generic recognition distinct from Siphonophora. 



A second genus of Siphonophoridae was found in San Benito 

 County, Calif., in November, 1926. This genus is remarkable be- 

 cause the mouth parts are not produced into a beak, because of the 

 extreme slenderness of the body, and because of the very large num- 

 bers of segments, in this respect probably exceeding any other 



milliped. 



SIPHONACME, new genus 



Type. — Siphonacme lyttoni, a new species from Arizona. 



Diagnosis. — Closely related to Siphonophora but differing in hav- 

 ing the posterior gonopods very slender and the distal joint of both 

 anterior and posterior gonopods nearly straight, as long or longer 

 than the preceding joints taken together. Also the head is broadly 

 oval and the beak relatively short, slender, and abrupt. 



Description. — Body slender, from twenty to thirty times as long 

 as broad, rather strongly convex. 



Head subglobose-pyriform, abruptly contracted to a short slender 

 beak. Antennae short, crassate, subclavate, a sense organ present 

 near the margin, on the outer face of the fifth joint. 



First segment oblong with anterior margin transverse or but 

 slightly emarginate. Segments rather strongly convex; anterior 

 and posterior subsegments tuberculate, the latter hirsute, with the 

 hairs rising from between the tubercles. 



Repugnatorial pores opening from a slight but abrupt prominence 

 on the dorsal surface close to the lateral margin; the orifice of the 

 pore surrounded by a fine rim bordered by a series of short, erect, 

 closely placed hairs. On a few of the anterior segments the pore is 

 near the front margin of the posterior subsegment, but on the other 

 segments it is near the posterior margin and almost in the angle. 

 Pleurae scarcely exceeded by the dorsal plates at the lateral margin. 



Last segment with pleural and ventral sutures fused; the ventral 

 suture open on the penultimate segment. 



Preanal scale distinct. 



