50 AUSTRALASIAN ANTARCTIC EXPEDITION. 
Four, including the type, October 4th, 1912, from 25 fathoms, Commonwealth Bay. 
The Australian M. commensalis Tate, is somewhat like this species, but is broader on the 
last whorl. 
Named in honour of Mr. C. F. Laseron, who did excellent scientific work for the 
expedition. i 
STILIFER POLARIS sp. nov. 
(Plate VII., fig. 80.) 
Shell conic-acuminate, thin, translucent, spire gradate, tapering to an attenuate 
mucronate apex. Whorls nine, mostly flattened at the suture and rounded at the 
periphery, last subglobose. Colour milk-white. Surface very glossy, narrow and 
faint spiral grooves are crossed by fine radiating hair lines. Aperture reniform, 
columella perpendicular, thickened and reflected, outer lip forwardly sinuate, thin- 
edged, anterior margin round and slightly everted, no callus on inner lip. Length, 
10; breadth, 6mm. 
This form is related to S. petterdi Tate and May,* from which the slender spire 
readily distinguishes it. There is no information as to its occurrence, but it is probably 
parasitic on some echinoid. 
A single specimen with the animal complete, January 29th, 1914, from 325 
fathoms, ooze, off the Shackleton Ice-shelf, in South Lat. 65° 6’ and East Long. 96° 13’. 
TRICHOTROPIS ANTARCTICA Thiele. 
Trichotropis antarctica Thiele, Deutsch. Siidpol. Exped., xiii., 1912, p. 197, pl. xii., fig. 6’ 
pl. xv., fig. 21; Jd., Smith, “ Terra Nova” Exped., ii., Moll., 1915, p- 67, 
pl. i, fig. 6. ‘ 
Four, December 28th, 1913, from 288 fathoms, off the Mertz Glacier, Adelie Land, 
in South Lat. 66° 55’ and East Long. 145° 21’. 
TRICHOCONCHA MIRABILIS Smith. 
Trichoconcha mirabilis Smith, Nat. Antarct. Exped., ii., 1907, Moll., p: 6, pl. 1., figs. 7, 7B. 
Torelua mirabilhs Thiele, Deutsch. Siidpol. Exped., xiii., 1912, p. 197; Jd., Smith, 
“Terra Nova” Exped., ii., Moll., 1915, p. 68. 
When dried the shell of this species crumpled and collapsed like that of some New 
Zealand Paryphanta. The extremes of distribution previously recorded are connected 
by the Mawson Expedition thus— 
One, December 31st, 1913, from 157 fathoms, ooze, off the Mertz Glacier Tongue, 
Adelie Land, in South Lat. 66° 32’ and East Long. 141° 39’. Hight, December 22nd, 
* Tate and May.—Trans. Roy. Soc. 8.A., xxiv., 1900, p. 97. 
