32 SUPPLEMENT TO THE 



Gemis — Spirifera, Soio., 1815. 

 I have not mucli to add with respect to the species of this genus. 



18. Spirifera curvata, Sc/dotheim. Dav., Dev. Mon., PI. IV, figs. 29—3.2. PI. IX, figs. 



26, 27 ; and Dev. Sup., PI. I, fig. 34, PL II, 



fig. 4. 



This remarkable and variable species has been described at p. 39 of my 'Devonian 

 Monograph.' Since then the Rev. Norman Glass has been able to develop its spiral 

 appendages, of which I give a figure. I have already alluded to the difficulty of sepa- 

 rating this species from Sp. gluhra. Palaeontologists relied on the shell-sculpture or 

 exterior markings as a distinctive character. In general the shell ^iSp. glabra is smooth, 

 or nearly so. In all well-preserved examples of Sp. curvata the surface is marked by 

 close equidistant concentric ridges. I have not yet detected on any specimen of Sp. 

 curvata the radiating interrupted raised lines, giving rise to concentric rows of adpressed 

 small flattened spines, similar to those that occur on the surface of well-preserved species 

 of Sp. lineata, Martin.^ It would be very diflScult to procure specimens of either species 

 showing the exterior sculpture in a perfect state of preservation. One or two weathered 

 specimens of Sp. lineata from the Middle Devonian of Hope's Nose, near Torquay (Sup., 

 PI. II, fig. 5, 5a), have shown indications of short broken spiny projections, but I 

 could not ascertain whether they were, as in the Carboniferous Sj). lineata, divided interiorly 

 into two canals. 



I must now refer the student to a very important paper by Prof. H. S. Williams, 

 entitled, " The Life History of Spirifer Icevis''^ in which the author endeavours to connect 

 by their surface- markings various species of Spirifera that had previously been considered 

 as specifically distinct. Early in 1881 Prof. Williams wrote and asked me to re-examine 

 the shell-surface of Sp. glabra. I accordingly did so, and found two examples of Martin's 

 species exhibiting concentric ridges and indistinct interrupted radiating lines ; but, as a 

 rule, the surface of Sp. glabra is quite smooth. Some time previously Mr. A. Champer- 

 nowne sent for my inspection a beautifully perfect specimen of Sp. glabra from Little 

 Island, Cork, covered with close equidistant rows of concentric ridges ; and this specimen 

 I found it impossible to distinguish from similar-shaped examples of Sp. curvata. I 

 therefore feel inclined to concur in the opinion expressed by Prof. Williams, that Sp. 



* ' Carboniferous Supplement,' p. 275. 



"^ ' Annals of the New York Academy of Science,' vol. ii, 1881. 



