10 



MARINE AND FISUERIEi^ 



6-7 EDWARD Vli., A. 1907 



Examples of a Pulvinulina and a Discorbina (PI. IV., figs. 1 and 2) were less un- 

 common, the former indeed very frequent in July and August, while a few examples 

 of a Spirillina (fig. 3) were observed in the latter month. A re-examination of these 

 after a study of the benthonic forms would render a closer diagnosis possible. 



RADIOLABIA. 



Very few members of this class were observed at Canso. Jorgensen records some 

 sixty species off the west coast of Norway, but only three of these were found at Canso. 

 It appears that they are commoner in the open ocean. Of those found, two belong to 

 Hseckel's group of the Acantharia and one to the Nassellaria. 



AcanfJwnia echinoides (Clap, and Lach.) HsBckel (PI. IV., fig. 4) was abundant 

 in August in both of the years si)ent at Canso. So abundant, that when sporulating 

 it could be seen in the form of distinct pink dots in the plankton. 



The second and much rarer Acantharian is Acanthostaurus palUdus (PI. TV., fig. 

 5) while the Nassellarian, only observed on two or three occasions, is the Plagiacantha 

 oracKnoides Clap. (fig. 6). 



INFUSORIA 01 LI AT A. 



This class is represented in the plankton chiefly by the family of the Tintinnidae, 

 a group exquisitely adapted for pelagic life. It belongs to the order Heterotricha, sub- 

 order, Oligotrichidea, in which the ciliary covering is reduced to a few specialized 

 tracts, that round the mouth being the most important. A genus, Strombidium, be- 

 longing to lanother family, Halteridae, is, however, met with under the siame circum- 

 stances, and shares the peculiar adoral series of membranellae. 



Stromhidium sulcatum (C. and L.) was described from salt water at Bergen, but 

 was observed to be very frequent at Canso in August, 1901. Its outline is somewhat 

 oval, but the posterior end is provided with certain characteristic furrows and the an- 

 terior with a projecting beak broader at its extremity than at its origin. The observed 

 dimensions were : 440 x 266/x. - > 



TINTINNIDAE. 



In discussing this interesting group of characteristic plankton Infusoria, I shall 

 follow the account given by Jorgensen in his recent discussion of the Norwegian 

 forms. (No. 6.) 



I have reproduced in Plate IV., fig. 7, the representation of the characteristic 

 ciliation of this group given by Lang in his Text-book (Protozoa, fig. 53). 



TiNTiNNUS — Schranh. 



This is characterized by the tubular case being open posteriorly. T. acuminatus 

 Clap, and Lach. (fig. 8) was seen only on one occasion, but it is readily recognized 

 by the ridges which occur on the posterior third of the case. The specimen observed 

 measured 258 x 17/x. T. ohliquus Clap, et Lach. (fig. 9) was only seen in July, both 

 in 1901 and 1902. Apart from its smaller dimensions (80 — 100 x 14 — 19//), it may 

 be recognized by the absence of the flaring anterior aperture. 



AMPHORELLA — Daday. 



This, like most of the other genera, has no posterior aperture. The commonest 

 species of this genus, A. suhulata (Ehrb.) Dad. (fig. 10), is exceedingly abundant in 

 the plankton in July and August. Its case is translucent, is furnished with a long 

 posterior spine and is at once recognizable by the series of denticulated rings which 



