94 PERMIAN FOSSILS. 



Perhaps the development of deltidial spines may only be a feature in those Strophalosias 

 with a large area, like that of Aidostoges Wangenhewii. SfropJialusia Gohlfussi has a 

 large area ; and its deltidium, as already noticed, possesses obscure indications of 

 irregular risings : perhaps the latter are rudimentary deltidial spines ? It will thus be 

 seen, if Aulosteges possess no other distinctive character than the one just noticed, tha 

 I am little disposed to regard it as distinct from Strophalosia. 



With respect to Dr. Geinitz's genus Orthothrix, it is obviously the same as 

 StropJialosia, the name of which claims adoption on account of its having nearly two 

 years priority of publication. 



Dr. de Koninck, in his ' Monographic du Genre Productus,' objects to the genus 

 Strophaloda on some very insufficient grounds ■} but it is singular that this gentleman, 

 in describing his Productus Buchianus, overlooked the area and teeth, which I readily 

 discovered on some specimens in the collection of Mr. T. Davidson. There is no 

 doubt on my mind of this shell being a true Strophalosia, a view completely proved by 

 the form of its reniform impressions. 



I may here advert to the interesting shell figured by Mr. J. de C. Sowerby in the 

 ' Mineral Conchology,' pi. 615, fig. 16 3 3, under the name qI Lqjtcena anomala. Mr. 

 Sowerby having very kindly permitted me to make an examination of the original of 

 these figures, I have been able to satisfy myself that it does not belong to Leptcena, 

 at least, limited as this genus must be, to forms represented by its type, the L. rugosa 

 of Dalman. Although I closely examined the specimen, I regret, from not being able 

 to observe any teeth, my inability to speak with certainty as to the genus in which it 

 ought to be placed. In its area and deltidium this shell corresponds with the genus 

 under consideration ; but until something is known of its internal characters, I feel 

 reluctant to make any more than this passing allusion to the agreement. 



I was formerly somewhat of the opinion that StropJialosia diflfered from Productus 

 in having both valves furnished with spines ;" but their occurrence on the same valve 

 oi Productus horridus (vide ante, p. 90), P. punctatus^ and some others,* shows that I 

 was premature in this respect. 



Perhaps what has just been noticed ought to induce some caution in repeating what 

 I formerly stated respecting there being " a slight but interesting difference between 



^ If the so-called Productus punctatus, \pith an area and a fissure, figured by Dr. de Koninck (Mon., 

 pi. xiii, fig. 2 b), as showing the futility of any genus founded on these characters, is really of the species 

 named, the argument amounts to nothing, as it is founded on merely an abnormal form. 



2 Vide Annals and Magazine of Natural History, vol. xviii, p. 28. 



^ M. de Verneuil notices the presence of points (petites piqures) on the flat valve of this species when 

 slightly deprived of a portion of its shell (vide Geol. Rus., vol. ii, p. 777)- I have a specimen exhibiting 

 the same valve furnished with spines as long and as crowded as they are on the large valve represented in 

 the work quoted, at figure 3, plate xvui. 



* Productus spinulosus (vide Min. Conch., pi. Ixviii, fig. 3) is stated to have its small valve furnished 

 with spines. 



