654 Memoirs of the Indian Museum. [Vol,. V, 



flocculent mud. The length of the animal varies from 1*5-3 mm. In a specimen 

 1/65 mm. long, the branchiae constituted "44 mm., the thorax 1 mm., and the 

 abdomen "25 mm. In a second specimen 23 mm. long, the branchiae were only 

 ■33 mm. in length. 



The branchiae (fig. 29A) consist of about 18-20 slender unbranched filaments 

 on each side (i.e. about 36-40 in all). Occasionally they present the appearance of 

 being arranged in groups attached to a short common stem, but this is probably due 

 to the contraction of the basal membrane. In appearance and structure they closely 

 resemble those of Manayunkia speciosa, as described and figured by L,eidy (1883, 

 p. 206, pi. ix, fig. 1). Within the circle of branchiae are two short clavate processes, 

 the "palps" or "prostomial tentacles." The body (fig. 29A) is cylindrical, and 

 consists of 13 segments, the first and last being without setae. The head is conical 

 in front, and bears two black eyes . There is a prominent collar, with an entire 

 convex border ventrally. Dorsally the ends of the collar are rounded and folded 

 inwards. The thorax consists of 8 setigerous segments, the anterior three being 

 short, but gradually increasing up to the 8th, which is the largest in the body. No 

 otocysts are present. There are 3 setigerous abdominal segments, and an achaetous 

 anal segment, the latter being usually spatulate, sometimes pear-shaped, and bearing 

 two black eyes. 



The ist thoracic segment has a bundle of 4 slender capillary setae on each side, 

 but no crochets. On the succeeding 7 segments there are on each side 2-4 dorsal 

 capillary setae, and 2-5 ventral crochets in a single row. The capillary setae 

 (fig. 29B) have short flattened blades and long slender tips. The crochets (fig. 29c) 

 are rather stout, with three teeth above the main hook. In the abdominal segments 

 the ventral bundles contain one or two very slender capillary setae (fig. 290), which 

 show only very slight flattening of the blade and no wings. The dorsal bundles 

 contain 9-11 crochets of peculiar form (fig. 29E). They are rather small, with 

 elongate shafts, and with numerous very fine long teeth, in several rows, at one end. 

 Beneath the teeth there is a slight swelling of the shaft or base of the crochet. 

 These setae closely resemble those of Haplobranchus aestuarinus, described and 

 figured by Bourne (1883, p. 171, pi. ix, fig. 14), and in a lesser degree, those of 

 Manayunkia and Fabricia. They are obviously intermediate in shape between the 

 elongate crochets of the thorax and the avicular uncini such as are found in Potamilla 

 and other genera (fig. 28k). 



The species agrees closely with the three genera Fabricia, Manayunkia, and 

 Haplobranchus. The characters held in common are : (1) the possession of 11 seti- 

 gerous segments, 8 thoracic and 3 abdominal ; (2) the shape of the dorsal and ventral 

 setae in the thoracic segments ; (3) the peculiar elongate crochets in the abdominal 

 segments; (4) the presence of eyes on the first segment; (5) and the absence of 

 otocysts. The present species agrees with Manayunkia in having a well-developed 

 collar and unbranched branchiae, and differs in the presence of caudal eyes. It resem- 

 bles Fabricia in having caudal eyes, and differs in having unbranched branchiae and 

 a well-developed collar. It agrees with Haplobranchus in having unbranched 



