376 bulletin: museum of comparative zoology. 



paralleled in the large series of the only other Arctic Pleurobrachia, 

 P. pileus, which have been examined by Moser, and by the writer. 



Finally, Euplokamis australis Benham ( : 07) is apparently a Pleuro- 

 brachia, to judge from its tentacular sheaths. In form it resembles 

 the more cylindrical specimens of pileus, though it differs from speci- 

 mens of that species of corresponding size in having much shorter 

 tentacular sheaths, and longer ribs. But the fact that pileus is now 

 known from New Zealand suggests that australis is an extreme variant 

 of that unstable form. 



Pleurobrachia pileus Fabricius. var. bachei A. Agassiz. 



Pleurobrachia bachei A. Agassiz, in L. Agassiz, '60, p. 294; '65, p. 34; 

 Moser, :03, p. 6; Torrey, : 04, p. 46. 



Acapulco Harbor, surface, about one hundred and fifty specimens 

 from 2-4 mm. high. Also, off the coast of California, lat. 37° N., 

 long. 122° 20' W., 131 specimens, 7-12 mm. high. Puget Sound, three 

 specimens, 10 mm. high. Gulf of Georgia, one specimen, collected by 

 A. Agassiz, 1865. This example is now so much flattened that its 

 dimensions can not be determined. But it is large. 



The more important features of the series have been described 

 above. 



Hormiphora L. Agassiz. 



Hormiphora is closely allied to Pleurobrachia, from which it is 

 separable only by the fact that the tentacular bases and sheaths 

 lie close to the paragastric vessels, instead of mid-way between them 

 and the outer surface of the body. And I agree with Mayer (:12) 

 that it will probably be united with Pleurobrachia in the future. But 

 it may be retained temporarily until its members are better known. 



The collection contains so large a series of one species of this genus 

 (upwards of two hundred and sixty specimens) that it affords an oppor- 

 tunity to test the constancy of some of the characters on which the 

 various Hormiphoras are based. The latest account of the genus 

 is by Moser ( : 09) who recognizes no less than nine species, H. 

 hormiphora Gegenbaur ('56), 1 spatulata Chun, palmata Chun, and 



1 This species has universally been called H. plumosa, under which name L. Agassiz 

 ('60) made it the type species of the genus. But the specific name plumosa was not 

 proposed by Sars until 1857, while Gegenbaur had described it as Cydippe hormiphora 

 the year before. Under the International rules of zoological nomenclature the older 

 name must be used. 



