KR. BONNEVIE. 



[REP. OF THE "MICHAEL SARS" NORTH 



tr 



O 



Fig. 2. Radula-teeth of Peraclis reticulata: m.t median, l.t lateral, r.t rudimentary. 



In addition to the specific characters already known 

 from the shell, I shall here only mention the existence 

 within the mantle-margin of two peculiar cell-groups, 

 looking like sense-organs, one at the base of the ctenidium 

 (o. textfig. 1. C, C 1 ) and the other near the free margin 

 of the mantle to the right of the balancer (os.). The 

 position of the first organ is that of an osphradium, but 

 in structure it differs considerably from similar organs 

 found in other thecosomata. 



The radula of P. reticulata has the characteristic 

 formula of the genus (1) 1 — 1 — 1 (1). Its median teeth 

 are symmetrically denticled on both sides of the median 

 line, while the big irregularly spoon-shaped lateral teeth 

 are finely denticled on a limited part of one border 

 (textfig. 2). As a character of importance for a distinction 

 between different species of Peraclis I may mention that 

 in P. reticulata the denticled part of the lateral teeth 

 forms a low tongue-like protrusion (fig. 2, b). 



Geographical distribution. P. reticulata 

 seems to be a widely distributed inhabitant of warmer 

 waters. It has been taken in the Indo-Pacific ocean 

 (d'ORBiGNY, Souleyet, PeLSENEER, Tesch), along the Ame- 

 rican and African coasts of the Atlantic ocean (Dall, 

 Pelseneer), and in the Mediterranean (Fischer, Jeffreys, 

 Forbes, Monterosato, Oberwimmer). 



The results of the "Michael Sars" Expedition (see 

 the table) prove that P. reticulata, like some of the small 

 species of Limacina, occurs in svarms within the upper 

 layers of the ocean, while outside of these swarms its 

 occurrence is very scattered. It was found at three sta- 



tions, one specimen near Gibraltar (St. 23), 600 or 700 

 individuals near the Azores (St. 56), and one specimen 

 at St. 81 (Lat. 48° 2' N), the most northern locality where 

 it seems at yet to have been taken. 



Station 



23 



56 



81 



Date 



5 /5— % 



10 /6— ll /e 



12/, 



N 

 Position yj 



35° 32' 



7° T 



36° 53' 

 29° 47' 



48° 2' 

 39° 55' 



Depth in m. 



0— 50 



50—100 



100—250 



250—500 



500—750 



1 



650 

 10 



1 



Number of individuals of Peraclis reticulata. 



As will be seen from the table the big swarm of 

 P. reticulata (St. 56) was taken between 50 and 250 m., 

 and the same is true of the specimens from Sts. 23 and 81, 

 A few specimens were also found in the deep-sea samples 

 from St. 56, but probably these were caught during the 

 passage of the gear through the swarm in the surface layers. 



Peraclis diversa Monterosato. 

 Spinalis diversa Monterosato, 1875 (p. 50; pi. I, fig. 1 — 3). 

 ? Peraclis bispinosa Pelseneer, 1388 (p. 36; pi. I, fig. 9 — 10). 

 Peraclis reticulata var. diversa Dall, 1889 (p. 80). 

 Peracle diversa Locard, 1897 (p. 29; pi. I, fig. 4—6). 

 ? Peracle bispinosa Oberwimmer, 1898 (p. 589). 

 Peraclis retikulata Meisenheimer, 1905 (p. 12). 

 ? Peraclis brevispira Pelseneer, 1906 (p. 146; pi. 12, fig. 45, 

 46, 48, 49, 51). 



