PENNATULIDA. 55 



Protoptilum thomsoni Koll. 



PI. I, Figs. 4— S. 



Protoptilum Thomsoni Koll. Monogr. 1872, p. 373, PI. XXIV, Figs. 220 — 222. 



lofotcnsc Dan. & Kor. N. North-Atlantic Exp. Penn. 1884, p. 61, PI. II, Figs. 14—20. 



» mohni 63, » III, 1 — 7. 



» carinatum » >■> 65, » III, > 8 — 11. 



armatum 68, > IV, » 1 — 7. 



Of a Protoptzlum-sj)ecies which I refer to P. thomsoni of Kolliker, I have had for examination 

 three considerable fragments taken by the Michael Sars in the summer of 1902 ; these fragments I 

 have been able to compare with a specimen from the Skager Rak belonging to the Riksmnsenm 

 in Stockholm, and with the material of the Bergen Museum amongst which were the type-specimens 

 of the above named four ■■species.* of the North-Atlantic Expedition. 



The description of Kolliker is based on four considerable fragments of the rhachis; both the 

 upper and the lower end with the whole peduncle were wanting. Only the abaxial edge of the polyp- 

 calyx is free, and this edge is most frequently provided with four small points or teeth (to judge from 

 the figures 221 — 222, PI. XXIV, these teeth are as often wanting or slightly marked); the axial side 

 passes into the ccenenchyma, and downwards towards the peduncle the calyxes pass upon the whole 

 so very gradually into the rhachis, that their length cannot be determined exactly; the projecting 

 part itself, however, measures hardly more than 1.5 — 2 mm ; the calyx is richly provided with calcareous 

 spicules 0.36 — i.c>5 mm long and 0.027 — o.o66 mm broad. The zooids have an (incomplete, calyx supported 

 by calcareous needles which form a small point. The polyps are provided with a row of spicules 

 on the aboral side of the stem of the tentacles (o.n — o.ic/ 1 "" long, 0.01 — 0.04"™ broad). According to 

 Kolliker the arrangement of the polyps is difficult to define precisely; it may evidently be described 

 as two-rowed, i. e. two rows of polyps on either side of the median line of the colony (this line, 

 however, is only to be determined with difficulty on the ventral side); but K. prefers to describe the 

 arrangement as consisting of short oblique rows of three polyps on either side, being of opinion 

 that each of the dorsal polyps forms a group with the two lower polyps placed more ventrally; these 

 oblique rows would then have to be designated as ascending towards the dorsal side, whilst the 

 oblique rows (or the individuals of the wings) in the Pennatulids generally ascend towards the ventral 

 side. The zooids are found in large numbers, and everywhere on the rhachis between the polyp- 

 calyxes, with the exception of a streak along the dorsal surface of the rhachis. The colour is pink, 

 varying in intensity in the different specimens. 



In the Scandinavian specimens before me the calyx of the polyps is rather varying with 

 regard to the degree to which it projects from the rhachis ; this holds good with regard to different 

 specimens as well as to different places in one specimen; but the axial side to the very mouth is 

 always incorporated into the ccenenchyma. Thus the measurement of the length and breadth of the 

 calyx may give very different results; it is especially difficult to determine the lower end of the calyx. 

 The edge of the calyx is also varying, being often quite without teeth, often with one large 

 and several smaller and indistinct; the most frequent number seems to be three, and these variations 



