142 Proceedings of the Royal Irish Academy. 



Stylodrilus Hallissyi, n. sp.^ 

 Plate IX., fig. 8, A-G. 



These worms vary from 20 mm. when contracted to 50 mm. when expanded. 

 Individually they also vary very much in size. Their movements are decisive 

 and rapid, and distinguish them easily from the Tubificidee, with which they 

 are usually associated. The cuticle is smooth, or with rings of clear glands. 

 There is a longitudinal band of circular cells in a line with each pair of 

 setse, running along the whole body -length. The prostomium is conical, and 

 is thickly covered with colourless round glands. The setas are paired, and are 

 all distinctly bifid. The upper tooth (PJ. ix., fig. 8, a) is much smaller than the 

 lower one, and the node is in the distal half. The clitellum occupies segments 

 10-12. It is formed of oval cells full of round globules, with clear spaces 

 between them. The segments are composed of two rings, the larger of which 

 is 4-6 times as broad as the smaller one. In the anterior segments the 

 smaller ring is very narrow. 



The intestine is covered with greenish-brown bladder-like cells, which 

 commence in the 6th segment. The brain (fig. 8, b) is formed of two lobes, 

 which are shorter and broader than those of Stylodrilus gahretce Vejd. (28, 

 taf. XI., fig. 12). The two lobes are connected near the anterior end, so as to 

 make the anterior concavity shallow, the posterior one deep. 



The first nephridium has its funnel in the 6 th segment, and opens to the 

 exterior on the 7th. The second nephridium similarly occurs in segments 

 12 and 13. Behind this there is usually a pair of nephridia in each segment. 

 They are very long and much folded, and stretch through several segments 

 (fig. 8, c) . The funnel is rosette-shaped, and composed of several cells. Imme- 

 diately behind the septum there is a large glandular structure, brown in 

 colour. The first part of the ciliated duct which follows is long and folded. 

 The next part is invested by a covering of clear gland-cells, which the duct 

 pierces several times. This part of the nephridium is closely applied to the 

 ventral vessel. Transverse sections (fig. 8, e, e) show three or four ducts 

 piercing the glandular covering. The slender duct finally emerges, and runs 

 alongside the proximal portion up to the glandular swelling near the septum. 

 Here it branches off, and goes straight to the external pore. This glandular 

 structure has not been described in any other species of Stylodrilus. 



In 8. lieringianus Clapar^de (5, PI. 4, fig. 14) figures the nephridium as a 

 simple slender tube; and Benham (2, p. 211) states that in S. Vejdovshyi the 



1 This species is named after my friend, Mr. T. Hallissy, of the Irish Geological Survey, who 

 collected this and several other species for me at Ballyhaise, 



