ATLANT. DEEP-SEA EXPED. 1910. VOL. III]. 



PfEROPODA. 



Perac/is triacantha Fischer. 



Embolus triacanthus Fischer, 1880. 



Limacina triacantha Pelseneer. 1888 (p. 20; pi. I, fig. 1 — 2). 



Embolus triacanthus Dall, 1889 (p. 80). 



Protomedea triacantha l.ocard, 1897 (p. 27; pi. I, fig. 1 — 3). 



Limacina triacantha Tesch, 1904 (p. 10, 19). 



Peraclis triacantha Pelseneer, 1906 (p. 146; pi. 11 — 12). 



This species was known from empty shells only until 

 the expedition of the "Research", when a complete animal 

 was found and described by Pelseneer (1906). 



In the "Michael Sars" material I have found ten more 

 or less complete animals, an investigation of which has 

 on all principal points confirmed the results of Pelseneer. 



Station 



23 



53 



56 



92 



Date 



Vs— 75 



7e— 9 /e 



10 /6— "As 



23/ 7 _24 /7 



N 

 Position w ' 



35° 32' 



7° V 



34° 59' 



33° 1' 



36° 53' 



29° 47' 



48° 29' 

 13° 55' 



Depth in m. 



0— 50 



50-100 



100—250 



250—500 



3 



1 



1 



5 



Number of individuals of Peraclis triacantha. 



The mantle-margin has in this species a regu- 

 larly rounded outline (textfig. 1 A). In the lateral teeth 



of the radula the denticled part of the border protudes 

 like a semicircular lobe (textfig. 4). 



Geographical distribution. P. triacantha 

 has been recorded from the Atlantic ocean only — from 

 the European (Pelseneer, Locard) and from the American 

 coast (Dall); in his paper on "Biscayan Plankton (1906) 

 Pelseneer says, without further demonstration of the fact, 

 that P. triacantha "est repandue dans tout le N. Atlantique". 

 During the "Michael Sars" Expedition it was taken at 

 four stations near Gibraltar (St. 23), near the Azores (St. 53, 

 56), and at one station (92) in the open ocean, always in 

 depths of 50—500 metres. 



Procymbulia Meisenheimer (1905). 



The generic characters of Procymbulia were based 

 upon the investigation of a single individual without 

 shell brought home from the "Valdivia" Expedition and 

 described by Meisenheimer. Among these characters the 

 spirally twisted body proves the genus to belong to 

 the family of Limacinidae. Other characters are: 1) the 

 symmetrical tentacles without sheaths, 2) the proboscis, 

 3) the development of the fins into a broad swimming- 

 plate, and 4) the existence of three distinct visceral 

 ganglia— which all serve to prove that Procymbulia is 

 more nearly related to Peraclis than to Limacina, while 

 one character viz.: the ventral pallial cavity, 



A,* 



Fig. 5. Lateral teeth of the radula of Procymbulia michaelsarsi, r.t rudimentary tooth. 



