﻿Vol. 6 1.] SEQUENCE IN THE BBISIOL AREA. 287 



The nature of the outer wall and its relation to the septa are 

 points of strong resemblance to Zaphrentis, while the arching of 

 the tabula? suggests a Zaphrentis-like ancestor. 



It has already been suggested, in considering the evolution of 

 Lithostrotion, that, at the top of the Seminida-Zone and in the 

 succeeding Dibunophyllimi-Zone, Lithostrotion came under a general 

 Olisiophyllidan influence and gave rise, in one direction to the 

 Koninchophylla, and, in the other, to the Dibunophylla. 



Of the Dibunopliylla, the earlier examples, namely, Dibunophyllum 

 d and D. <p (the maxima of which occur in Dj), exhibit a compara- 

 tively-simple type of structure. On the other hand, Dibunophyllum \p, 

 Lonsdalia floriformis, and Axophyllum 0, all of which only attain 

 their maximum in D 2 , exhibit the most highly-specialized type of 

 ClisioplryHid-structure. The great development of the vesicular 

 peripheral zone in such a form as Lonsdalia floriformis would also 

 suggest the approach to the end of a line of evolution. 



' Clisiophyllum'' (Carcinophyllum) 0, which reaches its maximum 

 at the top of S 2 and the base of D,, presents a problem to which 

 there is as yet no solution. The well-developed peripheral zone and 

 the excrescence of ' roots ' in specimens from D 1? would suggest that 

 this form occurs there at the end of a line of evolution, rather 

 than at the beginning or in the middle of such a line. 



Whatever may have been its origin, it seems most probable that 

 both this form and Oampophyllum afT. Murchisoni (Proc. Bristol 

 Nat. Soc. n. s. vol. x, 1903, pi. i, fig. 5) had a common aucestry. 



(2) Notes on the Brachiopods. 

 Productus. 



Productus rassus, sp. nov. (PI. XXY, figs. 1 & 1 a.) 



Compare James Hall, 'Eleventh Annual Report of the State Geologist 

 New York, 1891 (1892) 'Introd. to the Study of Brachiopocla ' pt. i; 

 Productella costatula, Hall, p. 228 & pi. xxi, figs. 15-17 ; and Prodicciella 

 hystricida, Hall, pi. xxi, fig. 21. 



Description. — Form : that of a small specimen of Productus 

 cf. Martini (see below, p. 288). 



The convex valve is composed, in the neighbourhood of the 

 beak, of concentric bands which often imbricate ; the ribs are short 

 and discontinuous near the beak, but become continuous over the 

 anterior portion of the valve ; there are well-marked wrinkles on 

 the shoulders ; the spines are short, but very abundant ; not only do 

 they form the terminations of the short discontinuous ribs in the 

 beak-region, but they also project from the continuous ribs on the 

 anterior portion, usually in concentric rows. 



Resemblances. — So close is the general resemblance of 

 Productus bassus to Hall's species (cited above) from the Chemung 

 Group, that it seems highly probable that Pr. bassus also belongs 

 to the subgenus Productella ; I have, however, failed to find any 

 trace of area or teeth in our specimens. 



