252 T. A. STEPHENSON 



Halcampidae typically worjii-likc, iiioil- or less, but very changeable 

 in form (see Part 11. Text-fig. 7, c, D). There is a physa which may or 

 may not be retractile and wliieh has einelides in it (alway.s ?). The main 

 ])art of the body, or scapus, may be without suckers, or it Jiiay have 

 suckers to which sand adheres, so as to make a more or less dense cover- 

 ing. A clear external separation into capitulum. scapus, and physa is not 

 necessarily present. Some species have no sheath. iSonietimes the scajjus 

 has solid papillae. Tentacles retractile, eight to twelve or more (e.g. 

 thirty-two), their longitudinal iiiuscic ectodermal. .Sphincter weak 

 mesoglocal (see Part I, Text-fig. 1, and PI. 22, fig. 7). Mesenteries either 

 all macrocnemes, oi' else divided into macro- and microcnemes. Macro- 

 cnemes six pairs (rarely one or two additional unpaired ones) or fewer; 

 microcnemes if present variable in number (see Part 11, Text-hg. 8). 

 Species : 



Genotype, H. chrysanthell urn . Peach, Johnst., 1847, p. 220. 

 (See also Gosse, 1860, p. 247; Haddon. 1889, }). 335; Walton 

 and Ree.s, 1913, p. 65; Haddon. 1886. p. 1; Faurot. 1895, 

 p. 127 ; Stephenson, 1918 a, p. 9 ; 1920 a, p. 440.) 

 H. duodecimcirrata. iSars, 1851, p. 142; Carlgr., 1893, p. 38. 

 H. arctica. Carlgr., 1893, p. 45. 

 H. limnicola, Annan., 1915, p. 89. 

 H. aspera, 8teph., 1918 a. p. 10. 

 H. chilensis, McM., 1904, p. 223. 

 H. kerguelensis, Studer. 1878. p. 546. (See Kwietnicwski. 



1896.) 

 H. arenaria, Haddon. 1886, p. 616; 1889, p. 3.35. (See also 

 Walton and Rees, 1913, p. 66.) And probably others, 



I have been obliged to transfer H. aspera from Hal- 

 campoides to Halcampa, because on re-examination of 

 some sections of it I find appearances \vhicli I take to indicate 

 a mesogloeal sphincter. The reasons for my overlooking it in 

 my original investigation were that tliere is not much of it, 

 and it was not until I had subsequently examined several other 

 species with insignificant sphincters that I found out exactly 

 where one must look for it in a deeply introverted and some- 

 what twisted specimen such as mine was. I had only trans- 

 verse, and not the more serviceable longitudinal sections of 

 the region where it lies, being furtlier misled by mistaking 

 certain parts of the endodermal circular muscle for a slight 

 endodermal sphincter. There is also perhaps a fourteenth 



