HYDROMEDUSAE, SIPHONOPHORES, AND CTENOPHORES. 313 



All the records which can be safely referred to pensile, that is, the 

 examples in which we know that excretory papillae are lacking, are 

 from the Indo-Pacific; that is, the Maldives, the Philippines, the 

 Malay Archipelago, Tahiti, and Japan. 



AEQUOREA MACRODACTYLUM (Brandt) Bigelow. 



Plate 43, fig. 7. 



Mcsonema macrodactylum Brandt, 1835, p. 21; 1838, p. 359, pi. 4. Syno- 

 nymy, Bigelow 1909a, p. 174 ; Mayer 1910, p. 333. To the list given there 

 must be added the Polycanna purpurostoma of Agassiz and Mayer (1899), 

 which I formerly referred to pensile, for the reasons given above (p. 312) ; 

 likewise some of the specimens recorded by Vanhoffen (1911) as pensile. 



Aequorea macrodactylum — material examined. 



The general features of this species have been described in detail 

 by Maas (1905) and by me (1909a), and as its relationship to 

 Aequorea aequorea is discussed above (p. 310), we need only consider 

 here the constancy of the characters on which I base the separation of 

 macrodactylum from pensile and aequorea. 



The following table contains the statistics of all entire specimens of 

 macrodactylum yet recorded with the information that they have ex- 

 cretory papillae. It is to be observed that the identification of the 

 specimens here listed rests on the presence of papillae and of the 

 " macrodactylum " type of tentacular bulbs. Number of tentacles 

 or canals was not considered in making up the table. By following 

 this plan we can find out whether or not it is correlated with the two 

 structural characters, which are more important. 



Vanhoffen 's figure (1911, fig. 21) shows that the specimen from 

 which it was drawn belonged to macrodactylum as here defined ; and 

 his statement that the tentacle-bulbs usually have more or less notice- 

 able clasps (1911, p. 233) shows that the same was true of most of his 

 series. Unfortunately he gives no data as to absence or presence 

 of papillae, or of the structure of the bulbs in individual specimens. 

 Had he done so his data on the numbers of canals and tentacles in so 

 large a series would have been most valuable, to check the systematic 



