part 3] PROF. W. J. SOLLA.S ox SACCAMMTXA CAKTERI. 193 



9. Oil Saccammina CARTEiu Bradt, and the Minute Struc- 

 ture of the FoRAMiNiFERAL Shell. By Prof. William 

 Johnson Sollas, Sc.D., LL.D., F.B.S., F.G-.S. (Bead 

 February 23rd, 1921.) 



[Plate VII.] 



This remarkable foraminifer, which contributes so largely to the 

 formation of some of our Carboniferous Limestone beds, was first 

 described by H. B. Brady in 1871,^ and assigned by him to the 

 existing arenaceous genus Saccammina (Sars^). His views on its 

 structure and taxonomic affinities have been accepted w^ithout 

 question by all subsequent writers, and are embodied in our text- 

 books on palaeontology. Brady himself, however, was evidently 

 puzzled by certain features presented b}^ the structure of the shell ; 

 thus, in his latest description,^ after stating that the shell is 

 compact and arenaceous with a nearly smooth exterior, he remarks 

 (p. 60) of the interior surface that it 



' varies a good deal in different specimens,' sometimes being ' smooth or 

 roughened only by the projecting angles of the constituent sand-grains [and 

 at others] covered with a network of short delicate labyrinthic growths.' 



Of the minute structure of the shell he finds it 



' difficult to speak in positive terms, owing to peculiar conditions of infiltration.' 



Final 1}% he calls attention to certain 



• minute circular scars, too frequent and uniform not to have a meaning, [and 

 suggests] ... that they may result from the repair of an injury to the test.' 



As a specimen of the Saccammina Limestone, from the classic 

 locality of Elfhills in Northumberland, crowded with remains of 

 this organism, forms part of the teaching collection in the Uni- 

 versity of Oxford, it devolved upon me to make myself familiar 

 with its structure. jMy examination led me to recognize the fidelity 

 of Brady's description, and at the same time to find an explanation 

 for what had seemed anomalous. Whether the fossil is to be 

 classed with arenaceous forms or not is a difficult question, which 

 will be considered later. 



Weathered specimens, on which Brady's description seems chieflv 

 to have been based, show the labyrinthine structure to which he 

 refers very clearly, and as well the circular ' scars ' on the exterior. 

 The latter may be recognized at a glance as the familiar ' beekite,' 

 that form of chalcedony which, owing to its mode of growth, and 



^ H. B. Brady, 'On Saccammina Carteri' Ann. & Mag. Nat. Hist. ser. 4, 

 voL vii (1871) p. 177. 



^ S. Sars, ' Fortsatte Bemaerkninger over det Dyriske Livs Udbredning i 

 Havets Dybder ' Vidensk. Selsk. Forh. 1868, p. 248 ; 1871, p. 250. 



•^ H. B. Brady, ' Carboniferous & Permian Foraminifera ' Palseont. Soc. 

 Monogr. 1876, pp. 56-61. 



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