310 



Ол'к Paulsen. 



This species was found sparingly in few samples from the 

 pack-ice and the coastal water. 



Dis tri b. Arctic species, known from Spitzbergen and Iceland. 



12. Peridinium pyriforme Paulsen, Meddel, fra Kommis, for 

 Havundersøg. Ser. Plankton, Bd. 1, No. 5, 1907, p. 13, fig. 15; 

 Nord. Plankton p. 46, fig. 57. P. Steinii Jørgensen f. pyrî formis 

 Paulsen, Meddel. Kom. Havund. Ser. Plankton Bd. 1, No. 3. 1905, 

 p. 4, fig. 3d— e. 



Fig. 8 shows a species which was fairly common in some 

 of the samples taken in August 1908 in the open water out- 

 side the pack-ice, and which I 

 cannot refer to any other spe- 

 cies than P. pyriforme. Length 

 42— 52/^. It differs from P. breve 

 by the taller form, the irregular 

 position of the intercalary à, 

 which in P. breve is regular 

 (Broch 1. с.) and in the very 

 narrow rhomb-plate, but, as sta- 

 ted above, these two species are 

 pj closely allied to each other. 



On the other hand, our spe- 

 cies is nearly related to P. Steinii 

 Jørgensen. As to the arrange- 

 ment of the plates (see fig.8D, E) 

 they are nearly identical, so the precingular a is small, the rhomb- 

 plate] narrow, and the intercalary о has an oblique position (Kofoid in 

 Arch. f. Protistenk. 1909, Taf. 2; Broch, Spitzbergen Plankton p. 49, 

 Broch in Arch. f. Protistenk. 1910, fig. 4). Our species differs from 

 P. Steinii in its much thicker and shorter form and in the thecal 

 wall being reticulate and not porulate as in P. Steinii. Broch says 

 (Spitzb. PI., p. 49): "ein näheres Studium von Peridinium pyri- 

 forme wird möglicherweise zeigen, dass die Individuen dieser Art 

 nur kräftig entwickelte Exemplare von Peridinium Steini sind." On 

 the other hand, Kofoid (1. с. p. 39) declares P. pyriforme not to be 

 identical with P. Steinii. 



Anyhow, it seems to me to be the best to keep the two species 

 distinct at any rate provisionally until further evidences may come 

 to hand. 



Distrib. Boreal oceanic species, known from the northern Athmtic 

 and its tributaries. 



С W\/ D "■ "' E 



Fig. 8. Peridinium pijrifonuc. 37Г> t. m. 



