212 PROF. W. B. BENHAM OX AQUATIC [Nov. 3, 



Locality. Lake Taupo, North Island, New Zealand. Also one 

 individual from Lake Waikare, and some immature and imperfect 

 individuals from Lake Manapouri, in the South Island, belong to 

 this genus, but I am unable to say whether they are identical 

 with the above. 



Remarks. — This new genus appears to be most nearly allied to the 

 genus Branchiura Bedd. *, as extended by Michaelsen to include 

 '■'■ Ilyodrilus coccineus" Yejdovsky. But it will not j&t into this 

 wenus, chiefly on account of the structure of the atrium. 



In B. coccinea the spherical atrium is lined by a layer of 

 ciliated cells, outside which is a layer of vesicular cells, corre- 

 sponding to the compact " prostate " (Cement -driise) of Tuhifex, &c. 

 Apart from this fact, the general arrangement of the male 

 efferent apparatus is like that of the new genus : the thick sperm- 

 duct, and the short atrial-duct, with muscles at its base, forming 

 a slightly protuberant papilla. 



With this species, too, B. coccinea agrees in the presence of 

 copulatory chsetse on segment xi., but in the form of these there is 

 considerable difference : for in B. coccinea, according to fig. I'id^d^ 

 on pi. iv. of Stoic's memoir t, they are of two kinds, both sigmoid 

 and crochets ; while in the new species they are of neither of 

 these two forms, but simple pointed, straight rods, with a nodal 

 swelling. There are other points of difierence, as in the undulating, 

 instead of simple, form of the commissural vessels, in the position 

 of the spermathecal pore, and the presence, in Taupodrilus, of a 

 distinct muscular duct. 



From B. sowerbyi there are more numerous differences, apart 

 from the presence in this species of the gills. 



So far as the atrium is concerned, the new genus exhibits 

 points of resemblance to Clitellio arenarius +, in which a thick 

 and relatively short sperm-duct enters the apex of an elongated, 

 dilated, glandular " atrium," which appears rather as a swelling in 

 the course of the duct. Of its minute structure we have no 

 account ; but in the total absence of a " prostate" there is a close 

 similarity to the hew genus. But in all other points there seems 

 to be no close affinity between the two, for there are no capilli- 

 form bristles in the dorsal bundles ; the chagtae being " only 

 forked " — both Beddard and Michaelsen give this as a generic 

 character. Further, two pairs of dilated hearts exist in segments 

 viii., ix. 



It is difficult to separate generic from specific characters, but 

 probably we may regard as in the former category : 



(ffl) the presence of fan-shaped chsetse dorsally ; 

 (6) presence of copiilatory cheetse on segment xi. ; 

 (c) character of the atrium. 



The structure of the atrium of B. coccinea has hitherto been 

 regarded as the simplest amongst the Tubificidae (Beddard, Monog. 



* Beddard, Quart. Journ. Micr. Sci. 1892, xxxiii. p. 325. 



, t Stole, Abhandl. Bohm. Ges. 1888. 

 X Of. Beddard, P. Z. S. 1888, p. 491. 



