POLYCH^ETA. 291 



unaccompanied by uncinigerons tori ; of these the third pair has not been noticed by 

 Grube (Plate V., fig. 125). On the dorsal side in the middle line, slightly in advance 

 of the first pair of fascicles, there is a peculiar nuchal organ flush with the surface of 

 the body (Plate V., fig. 125). The uncini are arranged in a polystichous manner in 

 the tori ; as many as 20 rows of peculiar minute uncini of a type best defined as 

 ammocharine ; when examined in situ they look like the separated teeth of multidentate 

 uncini. The capillary setae are linear, non-limbate, finely squamose towards the 

 acute apex. 



Tube tough, mucoid, encrusted with sand grains which are arranged with considerable 

 regularity in an imbricating manner. Wider in front, tapering behind, the tube is 

 much longer than the contained worm, being about 60 millims. The lips of the anterior 

 and posterior orifices are approximated at their respective ends, so that the openings 

 of the tube appear closed. The specimen was taken in company with Panthalis 

 mgromaculata. The structure and habits of the Ammocharidae form the subject of a 

 paper by Mr. Arnold T. Watson in ' Journ. Linn. Soc.,' Zoology, vol. xxviii., 1901, 

 pp. 230-260, plates 23-25. 



Family : CHvETOPTEKlD^E. 

 Chaetopterus appendiculatus, Grube Plate V., fig. 126. 



Grube, "Ann. Ceylon" (Holdsworth coll.), 'P. Zool. Soc. London,' 1874, p. 328. 

 Herdman, 'Ceylon Pearl Oyster Report,' Part I., 1903, p. 80. 



Locality : Station LXII., near Periya Paar, 7 to 13 fathoms. 



There are ten thoracic segments, the last two carrying uncinigerous tori and the 

 last bearing a large aliform notopodium. The penultimate thoracic tori are separated 

 by a deep median ventral notch ; the last thoracic tori are confluent across the 

 middle line. Uncini of the last thoracic torus mostly 6-dentate, some 5-dentate ; 

 uncini of a ventral abdominal torus 8 -dentate. 



In Grube's original description, which was based upon a large specimen 124 millims. 

 long, the tube measuring 364 millims. by 22 millims. in diameter, the uncini of the 

 posterior ventral tori are said to have nearly 20 teeth. This is a large number for 

 Chaetopterus, twice the normal number,* and might conceivably be due to the uncini 

 lying appressed, end to end, as they frequently do. 



Of the thoracic parapodia the first, fourth, and ninth are the shortest in the 

 specimen under examination. The fourth contains seven broad modified setae of the 

 type characteristic of the family. In this case these setae show a finely crenulate or 

 beaded distal border (Plate V., fig. 126). The fore-body of the specimen measures 

 5 "25 millims. long by 3 "5 millims. broad, hence much smaller than Marenzeller's 

 Ch. cautus from Japan, where the corresponding measurements were 20 millims. 

 by 10 millims., and there were 20 to 30 chaetopterine setae in the fourth parapodium. 



* Cf. Crossland, "Maldive Polychajta," 'P. Zool. Soc. London,' 1904, vol. i., p. 276. 



2 P 2 



