94 WILLIAM BLAXLAND BENHAM. 



SO also there are several points in which Diachseta shows a 

 resemblance to Perrier's genus, viz. in the similarly modified 

 first nephridiumj in the single elongated pair of seminal reser- 

 voirs (though they are in Diachseta very much longer than in 

 the other worm), and the single pair of " free" ciliated rosettes, 

 and in the position of the nephridiopores. But there are note- 

 worthy diff^erences between the two worms. In Diachseta 

 the body wall is thick, and not transparent. The anterior 

 extremity is not pointed, as in Urochseta, but much swollen 

 and obtuse. There are neither calciferous glands {'' glandes 

 de Morren^^) on the intestine, nor the pyriform sacs on the 

 body wall, nor '' intestinal hearts." The nephridia differ con- 

 siderably. The clitellum is longer than the area supposed by 

 Perrier to represent this structure in Urochseta (but certainly 

 this may diff'er in the same genus). 



The setae are all simple, and have not the bifid form charac- 

 teristic of Urochseta; they alternate throughout the body/ 

 except the ventralmost, which remain in line. In Urochseta 

 these last alternate as the rest do ; but this happens only in 

 the posterior part of the body. It seems, then, that this new 

 worm is very closely allied to Urochseta, and in any classifi- 

 cation would have to be placed very near to it among the 

 lutraclitelliani. 



Trigaster Lankesteri, nov. gen. et sp. 



This worm, like Diachseta, comes from St. Thomas and 

 belongs to the group Intraclitelliani. The single speci- 

 men was incomplete, as the hinder part was wanting. Professor 

 Ray Lankester had opened it and made sketches of it. 



The most striking point externally is the presence of a deep 

 median ventral fossa, situated in the anterior region of the 

 clitellum ; this fossa is bounded on each side by a couple of 

 papillse ; the whole arrangement is doubtless used in copulation. 



This worm possesses three distinct gizzards, separated from 

 one another by oesophageal regions ; it is this character that 



' In the genera Pontoscolex, Scbm., and Geogenia, Kinb., a similar 

 alternation of the setae is present in certain regions of the body. 



