ZooL.— Vol. II.] RISEN— OLIGOCH.^TA. 197 



Blood-vessels and Hearts. — The dorsal vessel is single. 

 There are three pairs of muscular vessels in somites X, XI 

 and XII, which probably serve as hearts. They are not 

 greatly extended, nor are they divided into pulsating cham- 

 bers separated by valves, as in D. Keyesi. The hearts are 

 covered by chloragogen cells. The dorsal vessel is simi- 

 larly covered. The blood-sinus in the dorsal part of the 

 intestine in X, XI and XII rises above the muscular layers 

 of the intestine and forms a kind of supraintestinal vessel. 

 In none of these somites is this vessel so free as in D. Udei, 

 being everywhere attached to the intestine, though elevated 

 above it. In D, Udei the part in XII is entirely separated, 

 while the one in XI is only superposed on the intestine. 



Intestine. — There are no dilations of the oesophagus. 

 The sacculated intestine commences in XVII. There is a 

 typhlosole in XX-XIV. 



Subgenus Naillenia, subgen. nov. 

 Diplocardia (Naillenia) Koebeli, sp. nov. 



Plate XIV, Figs. 177, 178. 



Definition. — Size 80-100 mm. by 2 mm. Somites about 100. Prostomium 

 divides somite I about one-half. Dorsal pores, VII/VIII. Spermiducal 

 pores in XVIII. Spermathecal pores in VIII and IX, both pairs postseptal. 

 Spermathecal sexual setae in IX. Penial setae large, curved in XVII and 

 XIX; sculptured, with spines. Exterior papillae, one pair on IX, one large 

 median papilla covering posterior part of X and anterior part of XI ; a large 

 median papilla on XIV and XV; a large median papilla between XIII and 

 XXIV. Sacculated intestine commences in XIV, thence to XXIII it possesses 

 an interior thick and greatly folded epithelium. Spermathecee large, with a very 

 large and thick diverticle directed forwards. Prostates thick and long, each 

 occupying at least two somites, opening into XVII and XIX. 



Septal formula: — 



V/VI, VI/VII, VII/VIII, VIII/IX, IX/X, X/XI, XI/XII, XII/XIII. 



Habitat. — About a dozen specimens, of which five were 

 adult, taken by Professor Albert Koebele at Morelos, 

 Mexico, at an altitude of 6,000 to 7,000 feet, in the region 

 of the pines, September, 1897. Though otherwise fully 

 developed sexually, none of the specimens possess a 

 clitellum. 



