POLYCH^ETA. 317 



In a typical example such as that figured on Plate VII., fig. 186, the total height 

 of the tube in the region of the orifice is about 6 millims., of which the crest occupies 

 1 millim. The operculum is sometimes dextral, sometimes sinistral in position, and 

 at the corresponding point on the other side, as noted by von Marenzeller, there is 

 usually a rudimentary operculum. Minute tubercles are sparsely distributed on the 

 concave opercular disc. 



Serpula watsoni, n. sp. Plate VII., fig. 187, and Plate VIII., fig. 6. 



Locality : Trincomalee, February, 1902. 



I have much pleasure in dedicating this species to Mr. Arnold T. Watson, whose 

 drawing illustrates it (Plate VIII., fig. 6). It is characterised by the great length of 

 the ampulla of the operculum, 3 millims., slightly exceeding the length of the style, 

 the total length of the operculum being 5 - 5 millims. The ampulla is about twice the 

 length of that portion of the style which rises above the collar. The disc of the 

 ampulla is traversed by about 25 rays. There are about 30 radioles in each gill. 

 The collar is entire below, divided on each side by an incisura lateralis. Uncini 

 from the last thoracic torus with 5 and 6 teeth (Plate VII., fig. 187). 



Spirobranchus cervicornis, n. sp. Plate VII., figs. 188 to 192. 



One specimen in bottle with Loimia vaiiegata, Dasyckone cingulata, &c. [? Gheval]. 



Total length 22 millims., made up as follows : Gill-apparatus (including operculum) 

 7 millims., thorax 5 millims., abdomen 10 millims. Width of thorax 4 '5 millims. 

 The gills diverge outwards ; the gill-rays (radioles) are rolled inwards at the top and 

 are disposed in a spiral of one turn and a half, about 30 in each gill. The thorax 

 consists of seven setigerous segments with six pairs of uncinigerous tori. The first 

 segment is produced into a capacious collar open above, its dorsal ends overlapping 

 and covering the expanded style of the operculum, nearly reaching to the disc 

 (Plate VII., fig. 188). Ventrally the collar-membrane is produced forwards as a 

 tongue-like process between the gills (Plate VII., fig. 189). The buccal seta? (of the 

 first fascicle) are of two kinds, long, slender, capillary setse fringed with hair-like 

 striae though without a definite limbus ; towards the tips of the setae the marginal 

 hairs project; secondly, stouter bayonet setse with pilose extremities (Plate VII. , 

 fig. 191). The remaining thoracic setse are of the common limbate type and call for 

 no remark ; there are two groups of different sizes, more slender and stouter, in each 

 fascicle. Thoracic uncini with fifteen teeth and a basal T-shaped mucro (Plate VII., 

 fig. 192). The abdominal setse are of the kind called " Dutenborsten " [geniculate 

 setse] by von Marenzeller (' Siidjap. Ann.,' ii., Taf. iv., fig. 46). 



In S. cervicornis the horns of the operculum resemble a pair of antlers, of which 

 the dorsal tine is half the length of the main tine (Plate VII., fig. 190). They only 

 differ in proportion from the horns of Spirobranchus giganteus as figured by Morch 

 (1803) and Ehlehs (1887). 



