288 Transactions of the Society. 



membrane between the teeth. Forked setse of ventral anterior 

 bundles usually three, with upper tooth considerably larger than 

 the lower. Forked setpe behind the girdle quite different in shape, 

 and very robust. These gradually change about segments 8-11, 

 so that whilst those in front of segment 8 have a character of their ' 

 own, the posterior form begins immediately behind the girdle ; 

 thenceforth never more than two fully developed setse are found in 

 ventral and dorsal bundles. There are no pectinate setse, and no 

 penial setae, but the normal forms occur iu the region of the body 

 which contains the sexual organs and pores. 



This is a specially well-marked species, but the working out of 

 so much new material has rendered it impossible for me to note all 

 the details hitherto. The setae are so characteristic, however, that 

 by their aid alone I can instantly distinguish the worm from every 

 other species. 



First definite record, Ledbury, Herefordshire, Easter Monday, 

 1911 ; since found in several parts of the country. 



5. Ilyodrilus jjallesceiis sj). n. 



One, or rarely two hair (capilliform) setae, and two, or rarely three 

 forked in anterior dorsal bundles ; from segment 15 the capilliform 

 setae gradually shorten and die out. The dorsal forked setae have 

 equal teeth, and possibly a delicate membrane, as in /. rohustus. 

 The teeth are not sharp pointed as in the ventral bundles, where 

 there are two setffi in the anterior portion of the body, with large 

 upper tooth. The posterior setae also have a large upper tooth, and 

 difter entirely from those of /. robust us in shape, size, and number. 

 One seta for each set, dorsal and ventral, behind. Head blunt or 

 pointed, according to tension. Chloragogen cells begin in 6. Blood- 

 vessels elaborate, enlarged about 7, 8, 9. Long duct in 13. Ante- 

 septal of nephridia consisting of a small funnel, with very active 

 cilia. 



Not yet found in the adult stage. June 15, 1911, Piston Hills, 

 Derbyshire; October 3rd, Stretton-eu-le-field ; Castle Gresley, and 

 elsewhere. 



Possibly the same as Bretscher's Tubifexfiliformis, though much 

 smaller. 1 give his description for the sake of comparison : — 



" Tuhife.r filiformis sp. n. 4-5 cm. lang, dabei fadenartig, 

 diinn. Borsten : Dorsal 1-2 Hakenborsten (fig. 4), ohne Mittel- 

 zahne, und 1-2 Haarborsten vou verschiedeuer Liinse; die langere 

 zwei mal liinger als die Hakenborsten und bedeutend diinner. Die 

 Spitzen dieser letztern sind lang, stark abstehend, Schaft gerade, 

 drei mal Linger als der distale Spitzeuteil, der gegen jeden etwas 

 abgebogen ist. A^entral vom 2-3, hinten 1 Hakenborste. 



" Pulsirendes Seitengefiiss in 8. Die beiden vordersten Aste des 

 Ellckengefasses vereinigen in 4 zum Bauchgefass ; in den vordern 



