1897.] 



Friknd. — The Ttcbe-Formmg Worms. 



297 



setae are found seems not to be definite ; in one worm they appear to 

 extend further back than in another of the same species. Sometimes 

 they seem to be present in the hinder segments ; but this is a delusion 

 arising from a curious hair-like parasite. The longest setee are about 

 equal to the average diameter of the worm's body, (2) Forked or 

 uncinate setoe, found in all the ventral and some of the dorsal bundles. 

 They vary in number, but three or four seems to be the average. The 

 lower fork is the lesser ; a point of distinction which should be remem. 

 bered. (3) Pectinate setae intermixed with the capilliform in certain 

 segments in the neighbourhood of the vital organs. I do not think the 

 teeth can be made out with any lower power than a good one-quarter 

 inch objective. To be seen to advantage a one-sixth or one-eighth 

 should be employed (fig. i). This nicety is the more important because 

 such a genus as Ilyodriliis, for example, in many respects resembles 

 Tubifex so closely that the utmost care is necessary in the study of this 



Fig. I. Setal System of Fig. '2. Parasitic Rotifer on 



Tubifex (segment 10). tail of Ttibifex. 



form of seta. There is no chitinous penis as in Limnodrihcs and some 

 other genera. In the eighth segment the blood-vessels are enlarged so 

 as to form dilated hearts which are very conspicuous, and supply one 

 ready means of diagnosing the genus. Ivocality—Garden field, Tuam. 



Limnodrnus Udekemianus, Clap. 

 I^ocality — Ballintoy, July 7th, 1897. See p. 207. 



Heterochaeta costata, Clap. 

 Collected in the Connswater, Belfast, June, 1896. See p. d^. 



Psaminoryctes, sp. 



Antrim, June, 1896. Awaiting further examination. See page i02»' 



Hemitublfcx B^nedii (d'Uden). 

 From Dr. Trumbull, Malahide, 1896. (/. Nat., vol. v., p. 128). 



The material which I still have on hand will, I doubt not, 

 yield a few additions to this meagre list, but my time for these 



