OF SOUTHERN INDIA. 269 



forms, several of wliieli at the first glance certainly do not appear to have mucli in 

 common Avitli Solemija, but they are still less related to any other group of 

 recent or fossil shells. Most of them are very unsatisfactorily characterized, 

 and although I have recorded them here as indej)endent genera, I have done so 

 more with the view of exposing this insufficiency and drawing the attention of 

 palaeontologists to the gaps which have to be filled up, than with the intention of 

 supplying characters of genera by which one could be distinguished from the 

 other. The genera which I have enumerated here are Cleidophorus, FyrenonicBus, 

 SanguinolUes, Leptodomus, Orthonota, Anodontopsis, Sedgwickia, Dolabra, Gram- 

 my sia, and Sole III 1/(1. 



From what I have already stated it is clear that I cannot well account for the 

 classification of these various forms. All, so far as known, agree in the solenoid or 

 elongately oval inequilateral form, thin shell, and obsolete hinge-teeth. The 

 difiiculty is to find out in such fossil forms, as Sanguinolites or Orthonota, which side 

 is the anterior and which the posterior. Palaeontologists are invariably accustomed 

 to regard the longer side as the posterior ; the opposite is, however, certainly the 

 case in Solemija, and if this be also the case in the two last mentioned genera, they 

 could not be better classified in any other family than in this. The remainder 

 of the genera here correlated are more or less allied in form to Solemija, and thev 

 may fairly be taken as indicating passages from this family to the Astartidm 

 and CsASSATELLiD.E. Nothing but a very careful re-examination of all the 

 pala3ozoic forms can lead to a satisfactory settlement of the present contro- 

 versies to be met with in the various pala3ontological monographs. 



1. Cleidophorus, Hall, 1847, (Pal. of New York, i, p. 300). Shell elongated, 

 inequilateral, beaks small, sub-anterior, with a vertical rib in front of the beaks 

 and another parallel to the upper straight margin ; hinge-teeth none, or (according 

 to M'^Coy) sometimes with a "small cardinal tooth behind the beak;" type, 

 CI. plamdatus, Con., sp., from siliu'ian beds of America and Europe. 



M'Coy, who writes (Brit. Palaioz. foss., p. 273,) the name of the genus 

 Clidophorus, says that he finds from the examination of authentic specimens 

 King's Fleurophorus to be identical with Cleidophorus ; but unless King's figure 

 of the interior of both valves is shown to be very erroneous, such an identification 

 cannot be admitted. 



2. Pyrenomceus, Hall, 1852, (Pal. New^ York, ii, p. 87). Elongated, inequi- 

 lateral, anteriorly rounded, posteriorly attenuated and produced, concentrically 

 striato-sulcated on the surface ; beaks tumescent, anterior muscular impression 

 deep, sub-anterior, (posterior unknown) ; hinge apparently without teeth ; type, 

 P. cuneatus. Hall, from the so-called Clinton group (Middle Silurian) of North 

 America. If this genus is to be accepted at all, some of the species described by 

 M°Coy under the name of Axlmis must be referred to it. 



3. Sanguinolites, M'Coy, 1844, (Carb. foss., Ireland, p. 47, and Brit. Palseoz. 

 foss,, p. 276). Very elongated, with sub-parallel upper and lower margins, rounded 

 anteriorly, obliquely truncate posteriorly, with an oblique prominent ridge from 

 the beaks to the postero-inferior margin, very inequilateral, beaks slightly prominent. 



