42 CARBONIFEROUS LAMELLIBRANCHIATA. 



proved to be the left valve of a species previously described by M'Coy as Pecten 

 tabulatus. He also denned the genus Streblopteria, the type of which is S. laevigata, 

 and he retained Pecten and Amusium. De Koninck in 1885 referred the Pectiniform 

 shells from the Carboniferous Limestone of Belgium to Rutotia, Streblopteria, 

 Aviculopecten, Limatulina, and Entolium. Of these it seems that Rutotia is a 

 synonym of Eumicrotis, Meek, and Entolium of Syncyclonema, Meek. 



Still, however, the shells referred to Aviculopecten were evidently diverse in 

 character, and when describing the Lamellibranchs from the Devonian rocks of the 

 State of New York, Hall found it necessary to subdivide them, retaining Aviculo- 

 pecten for shells of the type of A. planoradiatus, M'Coy, with large well-formed 

 ears, but separating under the name of Pterinopecten shells with an anterior ear 

 only and a very long hinge-line, Lyriopecten for shells with a shorter hinge-line and 

 a small anterior ear, and Crenipecten for shells with a crenulated hinge-plate. This 

 was a good advance, and two at least of these new genera are represented in 

 Carboniferous times. 



Even thus Aviculopecten seems to me to include heterogeneous groups, and at 

 least the smooth shells described by Phillips as Pecten ellipticus and P. anisotus, with 

 very small posterior ears, should be removed. De Koninck placed the latter group 

 with Streblopteria, but this genus has no posterior ear, hence I propose to refer 

 smooth, ovate, Pecten-lnke shells, with a smooth, grooved hinge-line, well-marked 

 anterior ear, but short and small posterior ear, often showing flat colour-bands, to 

 Pseudamusium, H. and A. Adams, as restricted by Verrill. I have also found that 

 shells possessing characters of Amusium occur in Carboniferous times, and hence 

 refer certain species to this genus. 



I have also obtained from Carboniferous rocks a series of Pectiniform shells, 

 which I cannot refer to any described genus. One has the valves smooth and very 

 oblique, a very short hinge-line, the posterior part of the valves excavated, and the 

 right valve the more gibbose. For this I propose the name Obliquipecten. Speci- 

 mens occur at Settle, Castleton, and Narrowdale. 



The following genera of Pectiniform shells are retained in the family Pectinidas 

 on account of the well-marked anterior ear in the right valve of each of them : — 

 Aviculopecten, M'Coy ; Crenipecten, Hall ; Pterinopecten, Hall ; Obliquipecten, Hind ; 

 Pseudamusium, H. and A. Adams; Streblopteria, M'Coy; Eumicrotis, Meek; 

 Amusium, Klein ; and Syncyclonema, Meek. 



Palccolima and Limatulina are placed in the family Limida?, though I am not 

 sure that the former is not nearer to Spondylus than to Lima. As to species, 

 those of Sowerby are all retained, namely, Aviculopecten plicatus, Pterinopecten 

 papyraceus, and P. granosus. Fleming is responsible for A. dissimilis. Fourteen 

 of the species described by Phillips are retained ; one only, P. arenosus, the type 

 of wliieli has been lost, is regarded as the young form of A. dissimilis, Fleming. I 



