372 bulletin: museum of comparative zoology. 



to query the record of " rhododactyla" (= pileus) from the Black Sea 

 by Sovinsky 004). Mayer (:12, p. 13) suggests that some of the 

 Mediterranean records, and the record from Bermuda, may be based 

 on young larval Bolinopsis. But such a mistake could hardly be 

 made by anyone familiar with Ctenophores, for the tentacular 

 sheaths of Pleurobrachia separate it at a glance from young of any 

 of the Lobata. Larval Pleurobrachias so young that the tentacles 

 still lie on the surface of the body might, of course, be confused with 

 other larvae: but such criticism does not apply to the Mediterranean 

 specimens noted above, nor to Chun's specimens. 



We do not yet know whether the Mediterranean Pleurobrachias 

 ever reach the large size attained by their Atlantic relatives. It may 

 be that they represent a diminutive local race. Such races are not 

 unknown among pelagic coelenterates ; witness the progressive 

 decrease in size in Cyanea as we follow it from north to south along 

 the American coast. But such a difference alone does not warrant 

 specific separation, and therefore I have no hesitation in relegating 

 rhodopsis to the synonymy of pileus, of which it is at most a variety. 



II. Pleurobrachia pileus and bachei. Torrey believes that these 

 two are distinct. But Moser ( : 09) in her most recent discussion of 

 the subject, unequivocally unites them, on the grounds that the 

 slight difference mentioned by Torrey as distinctive of bachei, i. e. 

 long funnel-canal, small tentacular sheaths, and junction of adradial 

 and meridional canals aboral to the level of the funnel, are to be 

 explained as due to different states of contraction. The only detail 

 which she found difficult of explanation was Agassiz's statement 

 that the tentacular sheaths of bachei open oral to the level at which 

 the adradial canals open into the meridionals, instead of aboral to it, 

 as in Torrey's specimens and in pileus. But this difficulty is not a 

 real one because in one of Agassiz's original specimens, which I have 

 been able to study and which is still in good condition, the openings 

 of the sheaths bear precisely the same relation to the meridional canals 

 that they do in pileus. Perhaps the original account was drawn from a 

 violently contracted, or otherwise distorted example. 



Inasmuch as Moser uses geographic distribution as a further reason 

 for uniting the two species, I may point out that there is some confu- 

 sion in the localities mentioned by her. The "Gulf of Georgia," 

 given by A. Agassiz as the type locality for bachei is not, as she sup- 

 posed, the coast of the state of Georgia, on the east coast of America 

 and in about the same latitude as Bermuda, but is on the west coast, 

 between Vancouver Island and the mainland, lat. 49° N., long. 124° W. 



