308 CEYLON PEAEL OYSTER REPORT. 



The macroscopic characters by which the species may be recognised are the 

 occurrence of an arcuate oblique double row of modified setae in the first segment and 

 the rich dark-brown colour of the ventral shields of the abdominal region. The short 

 collar still retains a band of violet below ; it is entire, its dorsal border being slightly 

 concave, while its ventral border is produced forwards to a median point. The 

 cuspidate uncini which accompany the avicular uncini are called " Pickelborsten " by 

 von Marenzeller. 



Accompanying the typical individuals described above there is another specimen in 

 which the whole collar is violet except at the anterior border. It is in a state of 

 protraction, and the modified setae of the first segment are disposed in a slightly 

 undulating longitudinal ridge which stands out pale upon the violet background. 

 This specimen further shows violet vittse and scattered spots on the gills, but no eyes 

 are to be found ; the terminal filaments into which the cartilaginoid axes extend are 

 exceptionally long. The apparent absence of eyes is remarkable. The brown colour 

 of the abdominal scutes is missing ; only the anterior abdominal region is preserved. 



Dasychone cingulata, Grube Plate VII., figs. 170 to 173. 



Two specimens in bottle with Loimia variegata, Eu-pomatus, &c. [? Cheval Paar]. 



Total length 26 millims., gills 9 millims. to 10 millims., thorax 4 millims., width 

 3 millims. ; about 60 segments. Eight thoracic segments with eight fascicles and 

 seven tori, the capillary limbate setae of the first fascicle not different from the others. 

 In each gill 19 to 21 radioles, each provided with about 14 pairs of dorsal sty lodes 

 and eyes ; radioles subarticulate ; terminal filaments of moderate length. In a 

 thoracic fascicle there are 36 limbate setae (Plate VII., fig. 170), and in an abdominal 

 fascicle about half that number ; the setae issue in two bundles, upper and lower, 

 those of the latter are shorter and (especially in the abdominal region) have a 

 pronounced curvature, a broader limbus and a shorter flagellum (terminal filiform 

 portion). It may be explained that the term " radiole," as applied to a single shaft 

 or rhachis of the gills, is used here in the sense in which it has been employed by 

 Professor McIntosh. It corresponds to Grube's filum branchiale. The actual 

 branchial filaments which are borne upon a rhachis are the pinnae, to which Grube 

 applies the term radioli. Grube and McIntosh, therefore, use the term " radiole" in 

 different senses. Grube ('Ann. Semp.,' 1878, p. 259) describes the radioles (sensu 

 McIntosh) as longearticulate, which corresponds with the Ceylon specimen, and he 

 remarks further that there are about ten pinnae (branchial filaments) to each joint ; 

 this is also in accord with my observations (Plate VII., fig. 172). In the Ceylon 

 specimen the articulation of the radioles is faintly indicated and best seen under low 

 magnification. 



Dasychone, like Phyllodoce, occurs singly in collections, and nearly every tropical 

 specimen has proved to be a distinct species. Grube says that in Dasychone decora, 

 Sars, the number of radioles in each trill varies from 20 to 36. The uncini of 



