344 L. E. CKAWSHAY. 



of gills, and so far as can be ascertained 17 setigerous segments. The 

 only doubt as to the latter point concerns a few specimens that were 

 partly broken, and in which the number of segments is not quite clear. 

 The species is undoubtedly the Incolea venustula of Marenzeller (96) 

 and de St. Joseph (101). But whatever may be said of the justifica- 

 tion for Marenzeller's reference of this type to the TerchcUa vcmistula 

 of Montagu, with 3 pairs of gills, the evidence he quotes in favour of 

 his conclusion that the Nicolea zostcricola of Oersted, sec. Grube et Malm- 

 gren, is synonymous with venustula seems far from convincing, and his 

 view is not shared by de St. Joseph. Neither Marenzeller nor 

 de St. Joseph finds any departure in the examples of venustula personally 

 recorded by them respectively, from the typical condition of 2 pairs of 

 gills and 17 setigerous segments. Such also is the condition, probably 

 without exception, of the specimens recorded here. It is significant 

 that in Plymouth both types occur distinctly. Dr. Allen has found 

 zostcricola common within tide-marks in Plymouth Sound. Among 14 

 examples of his material recently examined, I have found the number 

 of seti<^erous segments invariably 15, excepting in one specimen which 

 was slightly damaged and in which, probably in consequence, only 14 

 were distinct. All of these are of small size, not exceeding (in spirit) 

 2 cm. in length. On the other hand, seven specimens of venustula 

 obtained by him from a position 32 miles S. of Start Point, in about 40 

 fathoms, have, without exception, 17 setigerous segments. Some of these 

 range as low as 2 cm. in length, so that the difference in the number of 

 such segments between the two types would seem to be independent of 

 size or age. 



These facts, and the occurrence of the two types near Plymouth 

 under different respective conditions, and apparently without varia- 

 tion in the characters mentioned, favour the view that they are specific- 

 ally distinct. In Plymouth at least, zostcricola appears to be essentially 

 a littoral form of comparatively slender habit and small size, while 

 venustula frequents the deeper water and assumes a stouter form and 

 larger size. The number of setigerous segments moreover, 15 in 

 zostcricola and 17 in venustula, may apparently be regarded as a suffi- 

 ciently stable character on which to separate the two species from one 

 another. 



Thelepus cincinnatus, Fabricius. 



At Positions 1, 3 (a few), 14 (one), 32 (one), 33 (two), 34, 35, 



43 (one each), 45 (three), 49 (one), 51 (two), 56, 60 (three each), 



64 (one), 70 (two). 

 Depth, 40-50 fath. 



