HYDROIDS OF THE ALLAN HANCOCK PACIFIC 

 EXPEDITIONS SINCE MARCH, 1938 



C. McLean Eraser 



Introduction 



In previous papers (numbers 1-4 in volume 4 of the Allan Hancock 

 Publications), all of the hydroids obtained in the Allan Hancock Pacific 

 Expeditions up to the end of March, 1938, that were readily available, 

 were considered. After that date there was continued activity in collecting 

 from the Velero III until the ship was taken over by the Navy in the 

 autumn of 1941. These activities were confined largely to the waters of 

 Southern California, the west coast of Lower California and the Gulf 

 of California. There was one longer trip in 1939, when the Velero III 

 was taken to Balboa, through the Panama Canal and eastward in the 

 Caribbean Sea as far as Trinidad (The Caribbean hydroids have been 

 written up in a separate paper). Since the Velero III was taken over, 

 collecting has not been very extensive. There has been occasional local 

 collecting, and in July and August, 1942, the Coos Bay region of the 

 Oregon coast was investigated to some extent. This collecting, and par- 

 ticularly that carried out from the Velero III has been veiy fruitful. If 

 the other marine animal groups are as well represented as the hydroids 

 are, the collections will form the basis for research for many a day. 



The hydroids, recognized as such, that were set aside at the time of 

 collecting, made an extensive collection of themselves, but this has been 

 greatly increased through the efforts of Dr. Irene McCulloch, and of 

 others working under her direction. A search for additional hydroids was 

 made throughout the general, marine collections, with notable success. 

 Accordingly, when the whole of the Hancock collection of hydroids, not 

 previously examined, was presented for examination, the amount of the 

 material was somewhat staggering. However, in time it was all examined, 

 and this paper has been prepared to report on the results. 



In covering this hydroid material, 2,250 separate identifications were 

 necessary. Eliminating the distribution duplicates, over 1,500 additional 

 distribution records were provided, enough to change the whole face of 

 distribution problems in the Eastern Pacific. The finding of new species 

 is always of considerable interest, of course, but here the importance of 

 such somewhat sinks into insignificance, when compared with the value 



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