Rev. N. Glass — Spiral of Spirifera glabra. 461 



VII. — On a New Form of Spiral in Spirifera glabra. 

 By the Rev. Norman Glass. 



IN Davidson's Monograph of the British Carboniferous Brachiopoda 

 (1857), p. 60, he gives the following specific characters of 

 Spirifera glabra : — " Very variable in shape and proportions ; trans- 

 versely oval, rarely as long or longer than wide. Valves almost 

 equally convex, with a mesial elevation or fold in the dorsal, and 

 a sinus in the ventral valve, Hinge-line much shorter than the 

 greatest width of the shell ; cardinal angles rounded ; beaks rather 

 approximate, that of the larger or ventral valve prominent, incurved, 

 and of moderate dimensions. A hinge-area in the dorsal valve, that 

 of the ventral one triangular and of moderate dimensions, with its 

 lateral margins more or less sharply defined ; fissure partially covered 

 by a pseudo-deltidium. The mesial fold in the dorsal valve is 

 either slightly and evenly convex, rising gradually from the lateral 

 portions of the valve, or abruptly elevated, with a longitudinal 

 depression along its middle, which is also at times reproduced in 

 the sinus of the ventral one. The spiral appendages are large, and 

 occupy the greater portion of the interior of the shell. Surface of 

 valves in general smooth, but sometimes a few obscure rounded ribs 

 may be observed on their lateral portions." 



In a note appended to the above Davidson says : — " I have already 

 had occasion to remark, at p. 81 of my General Introduction, that 

 in p. 189 of his 'Synopsis,' Professor McCoy has described and 

 represented the spiral appendages of Spirifera (Martinia) glabra so 

 small as only to occupy the rostral half of the shell, but this has 

 been proved incorrect ; for all specimens obtained in which the 

 spirals were preserved, have shown them to be as large as in any 

 other species of the genus." 



With the view of finally deciding this matter of dispute, Davidson, 

 previous to his publication of the Carboniferous Supplement in 1880, 

 desired me to obtain specimens of Sp. glabra in order to develop the 

 spirals. I was soon enabled to develop specimens of this species 

 showing the spirals occupying their usual space in the shell, but the 

 specimens thus successfully worked out were comparatively small, 

 and Davidson urgently pressed me if possible to work out some 

 larger specimens. Probably many of your readers are acquainted 

 with the farmhouse and the fields adjoining, which divide the top 

 of the Winnats near Castleton, in Derbyshire, from the high road 

 to Chapel-en-le-Frith. This place is vividly impressed upon my 

 memory in connection with my search for large specimens of Sp). 

 glabra — for it was here on a dark winter's night after one of my 

 endeavours that I fell into a snowdrift, and had a long and weary 

 search for the high road, which was so near, but which seemed to 

 me so far. However, my journey, as it proved, was not unsuccessful ; 

 for I had a specimen in my pocket which when developed greatly 

 pleased my friend Dr. Davidson. It was the largest specimen of 

 Sp. glabra I had worked out up to that time, and it is represented 



