266 W. D. Lang — On Stoumtopora antiqua. 



Frequency of Branching. 



Number of peristomes before dichotomy 1 ... ... 2 



,, ,, between dichotomies 1 and 2 ... 1-2 



2 and 3 ... 1-2 



,, ,, 3 and 4 ... 1-2 



Ratio of Length of Zocecium to Breadth, the latter being taken as 1. 

 Before dichotomy 1 j ., ,j^ 



Atdichotomyl ... "... ... l§-2i 



2 2-3" 



3 2-2^ 



4 1^2J 



Shape of Zocecium. 



-r>„n J- r, . T \ zocecium 1, cylindrical. 

 Before dichotomy 1 j ^^ 2, slightly pyriform. 



From dichotomy 1 to dichotomy 4, cylindrical. 



Ornamentation. Very slightly ribbed. 



IV. Stomatopora GEEGORri, sp. NOV. (PI. XIV, Fig. 10.) 



Mention was made above to the figures given by Terquem & Piette^ 

 of Stomatopora antiqua, Haime. And though only a small part of 

 the zoarium is drawn large enough to clearly show its characters 

 in detail, it appears, by taking what is to be seen in the larger 

 figure with the loose appearance of the branching in the smaller 

 figure, that this form is more primitive than Haime's type, and does 

 not exhibit branching after the intermediate type so soon, if at all, 

 in its life-history. 



Moreover, a specimen (B.M. D. 7470, zoarium 1) from the capri- 

 cornus zone of Cherrington, encrusting Montlivaltia Victorice, Duncan, 

 shows at its first dichotomy a more marked pyriformation than the 

 specimens of S. antiqua, mutation capricornensis, and resembles more 

 nearly a specimen (B.M. D. 2131) of S. dichotomoides (d'Orbigny). 

 Unfortunately more of the former specimen is not preserved, so it 

 is impossible to say whether its further branches showed the 

 characters of S. dichotomoides (d'Orbigny). Now the latter species, 

 an Inferior Oolite form, is more simple in its branching than 

 S. antiqua, Haime ; nor is there anything to show that this 

 simplicity of branching, which even in the distal dichotomies does 

 not proceed beyond Type I, is not primitive. The form, then, must 

 have had a Liassic ancestor with as simple a type of branching. 

 Terquem & Piette's figures of S. antiqua, Haime, supplies a possible 

 ancestor. This form, for which I propose the name S. Gregoryi, 

 would only differ from S. dichotomoides (d'Orbigny) in the pre- 

 Jurassic irregularity of branching and in the lesser pyriformation 

 of the zooecia. Since the former character was lost and regular 

 branching was acquired during the Pliensbachian time by S. antiqua, 

 Haime, it is quite likely that the specimen mentioned above 

 (B.M. D. 7470, zoarium 1) represents the proximal end of a zoarium 

 in this stage, and the form would be known, according to the system 

 advocated, as S. Gregoryi, mutation capricornensis. The Sinemurian 



^ 0. Terquem et E. Piette : loc. cit., pi. xiv, fig. 32. 



