studies oil marine Oslratculs t>49 



of the unsymmetiical glauds. The careful investigation of the two forms dealt with below that 

 I carried out affords decided e%-idence that these two at least are very closelv related to each 

 other. Presumably the whole group is quite a natural one. 



Conchoecia rotundata G. W. MCller. 



Comhoeckt rotundata*, G. W. .Mlllei;, 1890 a, p. 275; pi. XXVIII. tigs. 41 — i3: 



pi. :^XIX, fig. 44. 



:, ... ,: 1906 a, p. S3: pi. XVII. figs. 23—34. 



,, „ „ 1906 b, p. 4. 



,, ,, „ 1908. p. 69. 



.. „ ., 1912, p. 77. 



(part?). (J. H. Fowl ej;, 1909. pp. 249. 273, 293; pi. XXIII and 



XXI \'. fiss. 205—224. 



Description: — vSee G. \\. MCLLKl;, 1890 a, p. 27.1. 1906 a. p. 83 and G. H. Fo\VLKli,luc. cii. 



Supplementary description: — Male: — 



Shell: — Length: According to G. \\. Mtl.i.Ki;. lS90a: l.l-i mm.; the siime author 

 writes on this point (1906 a): ,. i^ und S 0,8 — 1,75 mm., die tier Antarktis durchweg durch GroBe 

 (1,4 — 1,75 mm) vor denen der gemaCigten imd warmen Zonen (0,8 — 1.4 mm) ausgezeichnet": 

 Ct. H. Fowler, u.75 — 1,0 mm. The specimens investigiited by me measured 1.45 — 1,6 mm. Length : 

 height (in my specimens) about 2:1; length : breadth about 2,2 :1. Seen from the side the 

 shells of aU the specimens from the Antarctic Ocean investigated by me were of about the t\-pe 

 reproduced in the accompanpng fig. 1. i. e. they agreed fairly well with pi. XVII. fig. 26, G. W. 

 MCller, 1906 a (= ?) and with (;. H. FowLEI^'s fig. 205. For this character see p. 657 below. 

 Seen from beneath (see the accompanying fig. 2) it has its greatest width at or just 

 in front of the middle and the anterior part of the shell is in most cases somewhat larger than the 

 posterior part; it has fairly uniformly curved side contours, is rather broadly rounded anteriorly, 

 has an almost symmetrical rostrum and is somewhat pointed or narrowly roimded posteriorly. 

 The shoulder vault is weakly developed and rounded. The surface of the shell is 

 bare or has only a few very short hairs. Seen from inside: Selvage: This is comparatively 

 narrow, in most cases it has a whole margin on the rostrum and along the anterior margin of 

 the shell and the anterior half of the ventral margin of the shell and is exceedingly finely serru- 

 lated posteriorly. The selvage has no spine-like process on the rostrum. The glands are as 

 stated by G. W. MCLLER, 1906 a. The dorso-medial glands are somewhat weakly developed. 

 The glands along the posterior margin of the shell are also rather weakly developed; they have 

 their simple exits near the margin of the shell. There is no distinctly developed hinge-socket 

 or hinge-tooth at the posterior dorsal edge of the shell. 



* By a misprinl: rodiminhi. 



Zoolos. bidnij.', Upistla. Suppl. r>d. 1 '*- 



