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Show 1897.] PLANKTON OP THE FAEROE CHANNEL. 525 the second cirrhi (Borstencirrhen) were only 33 mm. long in this specimen, but in smaller ones were often longer than the body. The fully developed parapodia were .20 in number ; the undeveloped posterior part of the body carried eight rudimentary parapodia, and measured 9 m m . In the youngest specimens the parapodia were proportionately fewer than in the medium-sized specimens, and are again less crowded in the largest. Points like these, taken with the specific uncertainty already discussed, show how necessary is a renewed study of the genus on living material. I have not found any record of a larger specimen than this, but m y friend Mr. E. T. Browne informs m e that he has taken a specimen about 55 m m . in length off Valentia. As regards the horizontal distribution of the species, it is common dn northern seas, but not apparently further north than the Faeroe Channel. Here it was captured by both the ' Knight Errant' and the ' Triton,' and Prof. M'Intosh 1 points out that it appears to have been procured from very varying depths; this agrees with m y experience on the 'Eesearch'; it was taken at2 Sta. 13 #-465 to 335 fathoms, temp. 31° to 33° Fahr., and was also taken at the surface at a temperature of 54° F. TRACHELOTEUrms RIISEI (Steenstrup). I have found some difficulty in the determination of this species, owing probably to the fact that Steenstrup's original description 3 was of the briefest. A specimen obtained in the Faeroe Channel during the cruise of H.M.S. ' Knight Errant' in 1880 was fully described by Hoyle among the ' Challenger' Cephalopodai, but he expressed himself as uncertain of his determination. The deciding characteristics of the only two species5 known appear to be the following according to C a m s 6 (founded on Hoyle and Weiss) and Steenstrup :- riisei. behnii. ' Research' spec. Fins Rhomboid. O , S. Rounded behind. 0. Rounded behind. Heart-shaped. S. Heart-shaped. - ^ body length. C. >^ body length. C.7 =% body length. -^ body length. S. Tentacles =body length. 0. =§ body length. C. =body length. Arm 4... = | length of arms 2,3. S. =i length of arms 2,3. S. = f length of 2,3. While, then, the general dimensions of my specimen agree with 1 ' Challenger' Rep. Zool., Annelida Polychasta, xii. p. 532. 2 Cf Proc. Zool. Soc 1896, p. 993 note. 3 Vidensk. Medd. Nat. Foren. Kjobenhavn, (4) iii. p. 293. 4 Chall. Rep. Zool. xvi. Cephalopoda, pp. 163-166, pl. xxviii. figs. 6-12. 5 Since the above was in type, I find that a third species, T. guernei, has been described by Joubin (' Campagnes Scientifiques par S. A. le Prince de Monaco,' fasc. ix.), but it is not likely to be confounded with either of the other two. 6 Prodrom. Faunas Mediterr. ii. pp. 447, 448. 7 " Plus quam J pallii aequantes." Surely a mistake! PROC. ZOOL. Soc-1897, No. XXXV. 35 |
