THE 



GEO LOGICAL MAGAZINE 



NEW SERIES. DECADE V. VOL. X. 



No. III.— MARCH, 1913. 



I. — Notes on new or imperfectly known Chalk Polyzoa. 



By E. M. Brydone, F.G.S. 



[Continued from Vol. IX, p. 435.) 



(PLATE IV.) 



MxrCEONELLA (?) SPENCEKI, sp. IIOV. PI. IV, Eigs. .1 aiid 2. 



THIS species is very closely related to Macronella (?) Batlieri.^ 

 It is, however, generally on a much larger scale ; and the 

 single tube or paired tubes lying on or in the convex front wall are 

 very much larger in proportion and occupy nearly the wliole of the 

 front wall, with the result that they determine the general level of the 

 zoariura. The aperture is sunk deep below the general zoarial level 

 at the foot of the front-wall tube or tubes, and therefore much over- 

 shadowed by them ; it is semicircular, and has a small rounded tongue 

 projecting horizontally from its lower lip. More often than not 

 a small oceciura is present, but even that lies wholly below the 

 general zoarial surface and makes very little show. The rule that 

 a zocecium which begins a new line has one front- wall tube, while 

 a zocecium which lies in a line already established has a pair, is less 

 strict than in M. (?) Batheri, but is still a fairly general rule, 

 especially in the later stages of the zoai-ium. 



This species occurs chiefly in the zones of Offaster filula and 

 Act. quadratus, but occasionally in lower zones. Even when perfectly 

 preserved it is apt to be very vague and indefinite in aspect, and it is 

 anything but easy to recognize its structure ; after specimens have 

 suffered a little damage the deep cups in which the apertures lie take 

 on a very considerable resemblance to the open areas of ■d.Memhrani'pora, 

 and then its prominence to the naked eye relatively to its area is often 

 tlie surest indication of its true nature. The original figure of 

 M. (?) Batheri was inadequate, and I give a fresh figure of the type 

 for comparison. It seems hardly possible to assign these two species 

 satisfactorily to Mmronella., even if they can be brought within the 

 formal definition of that genus ; and if, as I strongly suspect, they 

 are allied to Cryptostoma gastroporum, Marss.,- they might well be 

 transferred to Marsson's genus. This point can hardly be determined 

 from figures only. 



1 Geol. Mag., 1906, pp. 289 et seq. 



- Die Bryo. d. Weiss. Schreibkr. d. Inseln Bugen, p. 96, taf. x, fig. 6. 



DECADE V. — VOL. X. — NO. in. 7 



