BRITISH SILURIAN BRACIIIOPODA. 99 



viously given in my ' Permian ' and ' Carboniferous ' Monographs, and in the ' Geological 

 Magazine' for January, 1881. The new details now given as to the shape and direction 

 of the primary lamellge near their origin, and also as to the shape of the accessory 

 lamellae, have been derived from the recent and extended researches of Mr. Glass. ■ 



The first description of the connections of the spirals in Athyris pectinifera was given 

 in my ' Permian Monograph,' in April, 1858 ; also I gave a description of the spirals and 

 connections of Athyris ambigua in my ' Carboniferous Monograph ' in April of the same 

 year. In vol. iv, pp. 282 — 290, of his ' Palaeontology of New York,' Professor Hall 

 described the connections of the spirals in Athyris spiriferoides and A. vittatn, and in 1880 

 Herr H. Zugmayer described the connections of the spirals of Athyris {Spiriyera) oxy- 

 colpos} Now, between the descriptions given by myself and Mr. Glass in their com- 

 pleted form, and those given by Hall and Zugmayer, there are some important differ- 

 ences. I may say that there is much more resemblance between the descriptions of 

 Zugmayer and my own than between the latter and those of Hall. The only points in 

 which Zugmayer's description differs from mine are — -first, that the accessory lamellae, and 

 the portion of the primary lamellae which is behind it, are represented by him as having 

 their lower edge denticulated ; second, that the primary lamellae are represented by 

 him as descending from the hinge-plate so far forward as to unite with the loop before 

 they curve backwards to follow the contour of the bottom of the dorsal valve. In subse- 

 quent correspondence with Zugmayer he has granted, on the inspection of my drawings, 

 that he is in error in relation to the second point, and that the representations I have 

 given are correct ; ^ so that the only difference remaining, and not a very important one, 

 is that in Zugmayer's figures of Athyris {Spiriyera) oxycolpos the accessory lamella and 

 the portion of the primary lamella which is behind it are denticulated. 



Herr Zugmayer has kindly forwarded to me two of his preparations of A. oxycolpos^ 

 one of which he regards as showing the denticulation of the lower edge of the accessory 

 lamella. Having sent the specimens to Mr. Glass, he writes to me that there is certainly 

 some appearance of denticulation in one of the specimens, but that it is not sufficiently 

 distinct to form the basis of a description, the appearance possibly being accidental and 

 due to peculiarities of the matrix. Mr. Glass is the more inclined to this opinion, because 

 one of the two specimens sent shows nothing of the denticulation of the accessory lamellae, 

 but closely resembles the preparations of our British A. plano-sulcata. Mr. Glass thinks, 

 however, and in this I quite agree with him, that possibly the denticulation may exist as 

 represented. It is to be hoped in his further researches Herr Zugmayer will add a 

 complete determination of this interesting point to the other valuable discoveries which 

 he has already made. 



^ ' Untersuchungen iiber Rhatisclie Bracbiopoden : Beitragen zur Palaontologie Oesterreich-Ungarns,' 

 von E. V, Mojsisovics und M. Neumayr, vol. i, pi. iii, figs. 2—23. 



2 Since the above was written Herr Zugmayer has corrected his little mistake in the ' Neues 

 Jahrbuch fur Mineralogie,' July, 1881 ; " tTber das Geriist von Spirigera oxycolpos, Emmr." 



