66 MR JAMES RITCHIE : SUPPLEMENTARY REPORT ON 



according to our present knowledge, by 68 different species, 21 of which are Gymnoblasts, 

 47 Calyptoblasts, while of the total, 36 must, so far, be regarded as peculiar to the 

 Antarctic region. As regards the number of individuals as distinct from variety of 

 species, recent results indicate that the area is a thinly populated one, for comparatively 

 few Hydroids were brought up in any one haul of trawl or dredge, a strong contrast' to 

 the abundance of tangled masses which occur in such temperate areas as the North Sea. 

 On the whole, the Antarctic Hydroid fauna may be looked upon as a rather meagre 

 one, comprising comparatively few species belonging to well-established genera. 



From the point of view of geographical distribution the collection to be described 

 is of a miscellaneous character, for Dr Bruce collected material on his outward 

 and homeward voyages as well as at his southern stations. Thus specimens from 

 tropical seas — from the Cape Verde Islands, from Brazil, and from St Helena — are 

 recorded alongside specimens from subantarctic and Antarctic localities, but so little 

 is known regarding the Hydroid fauna of those places that it seemed better to include 

 them here, at the same time furnishing a record of all the Hydroids brought together 

 by the Scotia. 



Two species, Thyroscyphus tridentatus and Plumularia lagenifera, hitherto recorded 

 only from the South and North Pacific respectively, have been found in the South 

 Atlantic, while the known ranges of several other species have been considerably 

 extended. 



Of new forms there have been described the trophosome and gonangium of 

 Sertularia heterodonta from off Brazil, the trophosomes of Antenella quadriaurita 

 from Gough Island, and of a variety of Lafoea gracillima from deep water to the 

 south of the South Orkneys, while the gonangia of Sertularia rathbuni and Anten- 

 nopsis scotix have been described for the first time. 



Some additions have been made to the existing descriptions of rare species, and 

 noteworthy variations have been recorded in the hope that the realisation of the con- 

 siderable limits within which variation is possible may tend to the better understanding 

 of reliable specific characters. 



I gladly seize this opportunity of setting right several unfortunate errors which 

 occurred in the earlier report on the Scotia Hydroids. There should be substituted 

 Hincks for Hinks, Lamarck for Lamark, Johnston for Johnstone, and Halecium for 

 Haleciun on p. 523. Aglaophenia dichotoma of the former report I now identify 

 with A. heterodonta, Jaderholm (infra, p. 96). 



In the following list, which takes the place of that in the original report, I have 

 included all the species collected by the Scottish expedition, those discussed in the 

 present paper being indicated by an asterisk : — 



