62 MR JAMES RITCHIE 



(4) Another new form, belonging to the genus Staurotheca, is also worthy of 

 mention as showing a development of the decussate arrangement of hydrothecee, which 

 necessitates a slight modification in the generic characters as originally described by 

 ALLMAN (1888, p. 75). 



(5) The occurrence among the specimens of the coppinia-gonosome of Grammaria, 

 which has only within the last few months been described by HARTLAUB (1905, 

 p. 597), is of interest, since the peculiar structure of this gonosome aggregate 

 necessitates the transference of the genus from the neighbourhood of the Sertulariidse, 

 where it had been placed by ALLMAN in 1888, to close proximity with the far-removed 

 Lafoeidse. 



(6) Throughout the genus Halecium, here represented by five species, the occurrence 

 of minute, translucent points round the rim of the hydrotheca has been noted (PL II. 

 fig. 5). These points, whose use ALLMAN did not happen to observe, are small, dome- 

 shaped thickenings on the inside of the perisarc, placed in a ring just above the base 

 of the hydrotheca, and to these are attached short strands from a disc-like portion at 

 the base of the polyp, which is thus moored to the walls of its insignificant hydrotheca. 

 Such refringent puncta are not confined to the Haleciidse, for similar structures in the 

 same position just above the floor of the hydrotheca were observed in the hydro- 

 thecse of Obelia geniculata. 



(7) The Scotia collection contributes also to our knowledge of the geographical 

 distribution of Hydroids. Thus to the already wide distribution, Arctic to Antarctic, 

 of such forms as Lafoea gracillima (Spitsbergen, Norwegian coasts, British coasts, 

 Magellan Straits, etc.) or Obelia geniculata (Norwegian coasts, British coasts, French 

 coasts, Kerguelen, etc.), still another locality is added, while several new records have 

 been made of the occurrence of less common forms. 



(8) As a remarkable case of associated distribution we may refer to Silicularia 

 hemisphterica, a simple Campanularian form, which has been recorded from three 

 different localities, namely, Falkland Islands (ALLMAN, 1888), Navarin Island, Tierra 

 del Fuego (HARTLAUB, 1905), and Gough Island (Scotia), and in each case it was found 

 in close association with Obelia geniculata. 



In classifying the specimens according to their geographical occurrence, the regions 

 mapped out by ORTMANN (1896) and made use of by Professor HARTLAUB (1904) have 

 been adopted. Taking these as our standard, we find that ten of our specimens fall into 

 the Antarctic Pelagic Region, all belonging to the Southern Subregion, while twenty- 

 nine, including all the new forms, have been found in the Antarctic Littoral Region. 

 The remaining two were obtained at St Helena. 



Before dealing with the systematic aspect of the collection, I should like to 

 express my special indebtedness to Professor HARTLAUB'S " Hydroiden der magal- 

 haensischen Region und chilenischen Kiiste" in the Zoologische Jahrbiicher (1905), 

 and to Professor NUTTING'S excellent monographs on the American Hydroids (1900 

 and 1904). 



(ROY. soc. KDIN. TRANS., VOL. XLV., 520.) 



