IV. FAMILIES UMBONULIDAE AND SMITTINIDAE 



Plates 19-35 



This fourth article on the Bryozoa collected by the U. S. Navy's 

 1947-^8 Antarctic Expedition discusses 16 species and subspecies, one 

 from the family Umbonulidae and 15 from the family Smittinidae. 

 Of these, only 5 have been previously described, the remaining 1 1 are 

 aew. Other species which in the past have been included among the 

 Smittinidae but which are now known to belong to other families 

 have been left for later papers in this series. 



In the case of new species, complete morphological data is given on 

 any structure which could be of taxonomic importance; in the case of 

 previously reported species, old descriptions have been augmented 

 wherever possible by new, additional data. The family Smittinidae 

 is one of especial difficulty because of the seemingly great variability of 

 its species. Moreover, over the years, the emphasis has changed on 

 what should be considered important or good diagnostic features, so 

 that it is not uncommon to find an old species description, sometimes 

 unaccompanied by a figure, which is so general that it will fit a large 

 number of related species just as easily as it will fit its own. 



The aims of this article are to present the range of variation of the 

 species, to depict the diagnostic features to the fullest degree, to add 

 ecological data, and, wherever possible, to compare the Antarctic 

 Bryozoa with closely related Bryozoa from other localities because 

 the Antarctic forms exhibit some unusual features that may be of 

 evolutionary or taxonomic significance if found to apply to groups 

 other than the Bryozoa. 



All illustrations were drawn with the aid of a camera lucida unless 

 otherwise stated in the captions. Measurements are based on 10 

 samples unless otherwise specified in the lists. 



Abbreviations used in lists op measurements 



Z-L, zooecial length (from proximal to 



distal end). 

 Z-W, zooecial width (at widest point) . 

 Z-H, zooecial height (from back wall to 



front wall). 

 Av-L, avicularia, total length (including 



both mandibular or beak and 



back areas). 

 Av-W, avicularia, width at widest point. 



B-L, beak length. (Where an avicu- 

 larial mandible is lacking it may 

 still be desirable to measure the 

 avicularial beak or space nor- 

 mally occupied by a mandible.) 



Pr-Or-L, primary orifice length, inside 

 measurement. 



Pr-Or-W, primary orifice width, inside 

 measurement. 



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