;108 Frederick Chapman: 



Observations. — The Victorian specimens here ascribed to a new 

 varietyi are midway between A. reticularis, L. sp., and .-1. imhri- 

 cata, Sow. sp.2. Although possessing the strong imbricating 

 lamellae of A. iinhricata, the well-marked fold and sinus so charac- 

 teristic of Sowerby's species is in most of the Victorian examples 

 nearly absent. In a few specifnens the latter feature is conspicuous 

 and more pronounced than in the type form A. reticularis, in whicli 

 the median area is broadly rounded and Avidely concave respectively. 

 The relationship of the variety decurrens to A. reticularis is seen 

 in the more acute and well-pronounced i-iblets and elongate form as 

 compared with A. imhricata. 



Occurrence. — Silurian (Yeringian). In mudstone; Loyola, near 

 Mansfield. Collected and presented by G. Sweet, Esq., F.G.S. Also 

 at Yering, Tapper Yarra, Victoria. Geol. Surv. Coll. 



Atrypa aspern., Sclilotheim sp. Plate XI., Fig. 14. 



Terebratula aspera, Schlotheim, 1813, Leonhard's Taschenbuch, 

 p. 74, pi. i., fig. 7; and Petrefactenkunde, 1820, pt. i., p. 263; pt. 

 ii., 1822, p. 68, pi. xviii., fig. 3. Atrijpa aspera, Schloth, sp.. 

 Dalman, 1827, Uppstallring och Beskrifning af de i Sverige funne 

 Terebratuliter ; Kongl. Vetenskaps Acadamiens Handlingar fiir an 

 1827, p. 128, pi. iv., fig. 3. Atrypa reticularis, L. sp., var. aspera, 

 Schloth., Davidson, 1865, Mon. Dev. Brach (Pal. Soc). pt. ii., p. 57. 

 pi. X., figs. 5-8. 



Observations. — in common with other components of the rich 

 Yeringian fauna of Victoria, tliis species is typical of the Devonian 

 elsewhere, both in N. Amei'ica and in England, and on tlie Con- 

 tinent. In N. America A. aspera var. occidentalis. Hall, occurs in 

 the Middle Devonian (Hamilton Shales); whilst the typical species 

 is found associated with Atrypa reticularis in the Middle Devonian 

 Limestone of Devon and Cornwall. A curious lithological factor in 

 regard to the distribution of this and the related foini, A. reticu- 

 laris, may here be noted, namely, the prevalence of A. aspera in the 

 mudstones and of A. reticularis in the limestones, of the Yei'ingian 

 "stage; although l)oth forms are occasionally found irrespectively of 

 lithological conditions. Tliis species has already Iteen noted from 

 both the Silurian and Devonian of Victoria by McCoy, who regarded 

 it as a variety of A. reticularis.^ 



1 The name decurreng denotes a decleiisiuii towards A. imbficata. 



2 Terebratula imbricata, Sowerby, 1839, in Mui-chison's Silurian System, pi. xiii., t\<^. 27. 

 Atrypa imbricala, Sowerby sp., Davidson, Jlon. Sil. Hrach. (I'.al. Soo.), pt. vii.. No. 1, \SiS7, \h Vi'', 

 pi. XV., figs. 3-8. 



3 Prod. Pal. Victoria, dec. v., 1877, p. •-'«. 



