6s Canadian Arctic Expedition, 1913-18 



Test from 0-3 to 1 mm. thick, pliable, translucent and vascular throughout. 

 The main vessel enters the test on the left side near the postero-ventral angle 

 of the body. The principal branches take almost parallel courses toward the 

 anterior end, except that a large vessel proceeds along the left side dorsally, 

 passes between the siphons, and, turning backward on the right side, breaks up 

 into four parallel branches and supplies nearly the whole of the antero-ventral 

 half of the test on that side. 



The tentacles number 66 and the prestigmatic zone is smooth. The dorsal 

 tubercle is in the form of a simple horseshoe, with the broad opening between 

 the horns directed forwards. The anterior lip of the peripharyngeal groove is 

 very broad near the tubercle, and partly covers the latter. The dorsal ganglion 

 is close to the tubercle. 



The dorsal lamina is ribbed on both sides as far as the oesophageal area, 

 but only on the left side farther .back. Its margin is coarsely toothed or lacin- 

 iate, the teeth corresponding to the ribs of the left side. There are occasional 

 intermediate teeth. The lamina extends a considerable distance behind the 

 oesophageal aperture. The accessory lamina on the right side of the oeso- 

 phageal area is ribbed on the right side and has teeth corresponding with the 

 ribs. The pharynx extends about 7 mm. behind the oesophageal aperture. 



There are 60 longitudinal bars on the right side, and 55 on the left. There 

 are small papillae at the junctions of bars and transverse vessels, and also inter- 

 mediate papillae in most parts of the pharyngeal wall. There are about two 

 longitudinal bars for each plication of the wall. The stigmata are three to six 

 in number for each mesh. 



The intestinal canal occupies nearly two-thirds of the left side of the body 

 from the posterior end forwards, and is much obscured by the rather thick 

 coating of closely placed renal vesicles. The stomach is short, broad, trans- 

 versely placed, and apparently with seven folds on the right side. The intestine 

 takes a rather evenly curved S-shaped course to end at the base of the atrial 

 siphon in the anus, which exhibits a bilobed reflexed margin. 



The complexly branched ovary is situated in the first intestinal loop and 

 extensively covers the right side of the first limb of the intestine, but extends 

 only slightly over the left side of the latter. Testes were not seen. The oviduct 

 crosses the last bend of the intestine, and then accompanies the rectum along 

 its dorsal side. 



Hartmeyer (1919, p. 131) has expressed a doubt as to the distinctness of 

 this species from A. prunum, and believes individuals of the latter species which 

 he has seen show intermediate conditions which connect the two. To the char- 

 acters which have been given by Hartmeyer (1903, p. 293) for distinguishing 

 the two species, I would add two, namely the presence of minute papillae scat- 

 tered generally over the surface of the test in A. dijmphniana and their absence 

 in A. prunum, and the number of longitudinal bars (15 to 20 on each side in 

 the latter, and more than 50 in the former). Although the two species may 

 tend to intergrade in other characters, it is suggested that in these two respects 

 they may always be distinguished. 



This record extends only slightly the known distribution of this species, 

 which has been found in the arctic seas to the north of Russia. However, 

 material collected by Dr. E. M. Kindle on the Labrador coast in 1921 contained 

 a single specimen of this species, whose distribution is doubtless fairly exten- 

 sive in the Atlantic portion of the arctic and sub-arctic regions. 



