DAVIDSON — ON BRITISH CARBONIFEROUS BRACHIOPODA. 



53 



modifications lead us gradually to Sp. rhomboidalis, which might also 

 be nothing more than a variety of Sp. glabra. I merely express here 

 on this and other questions the results of my own impressions or 

 personal observations, which may be more or less erroneous. Sp. TJrii 

 is a good little species, which I believe to be a recurrent form of the 

 Devonian, and present also in the Permian strata, notwithstanding 

 Prof. King's assertion to the contrary. 



Sp. Garlukiensis, as far as I know, is also distinct ; while Sp. Imeata 

 is another excellent species, but exceedingly variable in shape and 

 sculpture ; at one time I felt disposed to unite with it Sp. elliptica; but 

 having subsequently felt somewhat uncertain, have since preferred to 

 consider it provisionally separate. 



Sp. TJrii, Sp. Uneata, and I believe Sp. elliptica had their surfaces 

 closely covered with numerous small spines, and it is possible that 

 other forms were so invested. ^ 



Spiriferina. — Of this subgenus three species only appear to have 

 been properly distinguished, viz., Sp. laminosa, Sp. insculpta, and Sp. 

 cristata, var. octoplicata. Sp. minima has been established on one or two 

 specimens still very doubtfully characterized ; as all my efforts have 

 been unsuccessful in the endeavour to obtain more, I consider the 

 name hardly worth retaining. 



Gyrtina. — Of this subgenus two good species appear to exist, viz., 

 0. septosa and G. carbonaria, a third, G. dorsata, is somewhat doubt- 

 fully determined, on account of the imperfect material at my command, 

 which consisted of two fragments only from the Carboniferous 

 limestone of Cork, in Ireland. It would, therefore, be very desirable 

 that geologists in that locality should have a search for better speci- 

 mens. 



Rhynchonella. — Nine species are provisionally retained ; but the 

 claims of Rh. cordiformis have not been satisfactorily established ; and 

 of Rhynchonella ? gregaria but two imperfect valves have come under 

 my examination. Rhynchonella ? trilatera appears to be also a very 

 rare species, for I am acquainted with only a very few specimens 

 from Derbyshire, in the British Museum, and in that of the School 

 of Mines : it appears also to be a rare shell in Belgium. Rh. ? nana 

 and Rh. semisulcata are by far too doubtful to deserve more than a 

 passing notice ; and it is deeply to be regretted that palaeontologists 

 can bring themselves to fabricate species on such insufficient and 

 imperfect material, adding only confusion where such should be care- 

 fully avoided. 



Gamarophoria. — Pour species have been recorded ; but more 

 abundant and better material with reference to G. isorhyncha and 

 G. lateralis must be obtained before these can be definitely adopted. 

 Of the first I am acquainted with but a single imperfect example : 

 of the second, with those only in the Cambridge Museum. 



G. Grumena, Martin, is a well made out species, and evidently the 

 same as that from the Permian rocks known under the designation of 

 G. Schlotheimi ; and although I consider myself justified in referring 

 Terebratula rhomboidea and T. seminula of Phillips to the same 



