20 A Canadian Arctic Expedition, 1913-18 



Length of hingeline 9.5; of disk 24; height 22; max. diameter 5 mm. 



Station 43a. Dredged in about 50 fathoms, mud and pebbles in Dolphin 

 and Union strait, Northwest Territories. Many specimens. 



This species belonging to the group of P. vitreus, P. gronlandicus and their 

 allies, is distinguished from any of them by the entire absence of any regular 

 radial sculpture or ornamentation. Denude P. randolphi of the Pacific fauna of 

 its radial rows of minute prickles and it would approach the present species. 

 The only other quite smooth species of the group known to me, belongs to the 

 Magellanic fauna. 



The species is named after Dr. R. M. Anderson, chief of the Southern 

 Party, of the expedition. 



Catalogue Nos. 4235, 4236 (Ottawa). Types and co-types. 



Genus Macoma Leach. 

 Macoma oneilli, n. sp. (PI. II, fig. 1.) 



Shell small, thin, oval, compressed, inequilateral, slightly inequivalvr, tlu; 

 anterior part more than twice as long as the part behind the umbones; white 

 covered with a dehiscent yellowish-olive periostracum; beaks hardly perceptible, 

 ligament prominent, posterior end with an extremely narrow compressed dorsal 

 margin corresponding to the fold of most species; anterior and posterior ends 

 subequally rounded; dorsal and basal margins nearly equally arcuate; interior 

 chalky white, the hinge with two small but well-marked teeth in each valve, the 

 anterior left cardinal bifid; pallial sinus rounded behind, co'alescent below, a 

 little smaller in the right valve than in the other ; muscular impressions subequal 

 and of moderate size. Length of shell 21; length in front of the vertical from 

 the beaks 15; height 15; diameter 6 mm. Catalogue No. 4240 (Ottawa). 



Station 43a-6. Dredged in Dolphin and Union Strait in 30 to 50 fathoms, 

 mud and pebbles. Two specimens. 



This species is remarkable for its evenly oval shape and flattened valves, 

 devoid of the usual posterior twist. Among the various species of Macoma in 

 the Arctic seas it approaches nearest to M. moesta Deshayes, but is quite distinct 

 It is named in honour of Mr. J. J. O'Neill of the party. 



Genus Physa Draparnaud. 

 Physa jennessi, n. sp. (PI. II, fig. 2') 



Shell small, thin, of four whorls, of a dull amber yellow without a darker 

 streak behind the outer lip; apex rounded, rather blunt, surface polished with 

 occasional incremental irregularities and a microscopic spiral striation obsolete 

 in places; spire shorter than the aperture, the last whorl much the largest, the 

 suture not deep, the whorls moderately rounded; outer lip sharp, inner lip 

 slightly erased and whitened; pillar straight, thickened where it meets the body, 

 with a little depression behind it. Length 8 ; length of aperture 5 ; max. diameter 

 5 mm. 



Ponds near Bernard harbour, rare. Collected by Mr. D. Jenness of the 

 party, in whose honour it is named. Catalogue Nos. 4019, 4020 (Ottawa). 



This is remarkable as the most northern species known of the genus. By 

 some unexplained factor, perhaps connected with glaciation, the genus Physa 

 is not represented in the boreal region of Asia or America between the western 

 Siberian boundary and cape Bathurst. It occurs in southern Siberia among 

 the headwaters of the Amur river. In America the most northerly localities 

 reported are Moose Factory on Hudson bay, and Great Slave lake. The allied 

 genus Aplexa seems to take the place of Physa in all the boreal region above 

 referred to. When we consider that the large Lymnaeas of the type of L. stagnalis 



