AND ITS INTERNAL STRUCTURES. 317 



indicated by the shading. The feature is more plainly marked in 

 the outline woodcut upon p. 639 of Brady's Challenger monograph, 

 which was probably drawn by Hollick from a sketch by Brady. 

 The depressions between the lobes of the " float " chamber are 

 shown by lines in all the figures, notably in figure C, which shows 

 the form in optical section as seen from the base. From the 

 nature of the drawings, however, and from the entire absence of 

 any reference to the presence of an internal chamber, there can 

 be no doubt that Brady entirely misunderstood the meaning of 

 the markings which he saw, and it is probable that he regarded 

 these markings as thickenings of the balloon wall. 



7 



Cymhalopora {Tretomphalus) hulloides. 



a. Large surface- specimen ; h. small (young ?) specimens from the same 

 gathering ; c. distal face of the balloon-like chamber, showing the 

 entosolenian orifice, seated in a slight depression. 



(Reduced from Brady's report on the Foraminifera of the Challenger 

 Expedition.) 



I have been aware of the existence of this inner chamber for at 

 least ten or twelve years, but never having made any special study 

 of the form until I received Mr. Matthews' material, I was misled 

 by the woodcut in the Challenger report into the belief that it was 

 a well-known feature of the species. 



There is another feature in connection with this singular form 

 which does not seem to have received the attention which it 

 deserves. I refer to the existence of two distinct varieties which 

 may be described as the Discorbine and the A.cervuline forms. 

 In the Discorbine form the early chambers are regularly spiral, 

 and, apart from the final balloon, are indistinguishable from 



JouRN. Q. M. C, Series II. — No. 51. 21 



