BULIMINIDAE 129 



more inflated, and the sutural lines are generally marked by a series of punctae which are 

 apparently superficial and not apertures in the real sense, though if a canal exists along 

 the sutural line (which is probable although I have not been able to confirm its existence) 

 they would communicate with it. The chambers are arranged triserially, and the initial 

 end is usually more or less acutely pointed, as in the figured specimen from Australia 

 {ut supra), but sometimes bluntly rounded as in Sidebottom's fig. 5. These differences 

 probably mark the microspheric and megalospheric forms respectively. The test bears 

 a general resemblance to a Polymorphina of the group of P. communis. 



The known distribution of the species— Mediterranean, East Africa, East coast of 

 Australia — shows that this species has a wide range outside the Antarctic. 

 265. Delosina sutilis, sp.n. (Plate V, figs. 1-8). 



Delosina complexa (slender form), Wiesner («o« Sidebottom), 1931, FDSE, p. 123, pi. xxi, 

 fig- 254- 



Four stations: 170, 175, 363; WS 482. 



Test hyaline, thick-walled and finely perforate; ovate, bluntly rounded at the initial 

 extremity in the megalospheric form, the megalosphere being large and prominent; 

 abruptly pointed in the microspheric form; rounded in both forms at the terminal end. 

 The broadest point of the test is at about three-quarter length, in section it is nearly 

 circular at first, becoming oval with growth. The test consists of few chambers, up to ten 

 in number, arranged triserially with an increasing tendency to a biserial plan. Chambers 

 inflated, elongate, embracing, increasing rapidly in size, the last two or three forming the 

 bulk of the test. Sutures depressed, the marginal edge of each chamber slightly over- 

 lapping the edge of its predecessor. Parallel with the suture a line is visible along the 

 edge of each chamber which marks a canal in the thickness of the shell. From the canal 

 a number of short tubes extend to the edge of the overlap, where they terminate in 

 minute openings. These short tubes have the appearance of stitches sewing the two 

 chambers together. The terminal extremity of the shell bears a number of coarse punctae 

 like a sieve ; they are only superficial and do not pass through the wall ; the canal appears 

 to terminate in this sieve-like area, which represents the only approach to a general 

 aperture in the test. The test is smooth and highly polished, of the colour of old ivory, 

 sometimes with a pink tinge due to the underlying protoplasm, which in life fills all the 

 chambers and is pink in colour and quite devoid of stercomes or digestion products. 



Length of megalospheric specimens ranges up to i-i mm.; breadth up to 0-75 m. ; 

 thickness about o-6 mm. A microspheric specimen was 1-20 mm. long, 0-85 mm. in 

 greatest breadth. 



The distribution is confined to St. 363 in the South Sandwich Islands, where only 

 two specimens were seen, St. 170, off Clarence Island where many specimens were 

 obtained, and Sts. 175 and WS 482 in the Bransfield Strait, where the species was less 

 frequent than at St. 170. The maximum depth was 342 m. at St. 170. Delosina wiesneri 

 occurred in company with D. sutilis except at St. 175, but always very rarely. In the 

 Gauss material the frequencies are reversed, D. wiesneri being numerous and D. sutilis 

 very rare. 



Dx 17 



