belonging to the Class Palliobranchiata. 93 



The whole of the foregoing characters distinguish Strophalosia 

 from Productus, both of which agree in the form of their valves, 

 in their dorsal valve being beset with spines, and to a certain 

 extent in their internal structure*. 



Another apparent distinguishing character of Strophalosia con- 

 sists in its habit or mode of attachment : the flattened state of 

 the umbone, so general to the species, goes far to prove that they 

 were attached to foreign bodies by this part, as obtains in most 

 of the Thecideas ; further, several of my specimens of a magne- 

 sian limestone species are found under circumstances completely 

 proving, that in addition to an umbonal attachment, they adhered 

 to the inner surface of dead shells of Productus horridus by means 

 of long creeping spines f. 



The species which I purpose placing in the genus Strophalosia 

 are the following : Productus horrescens, Vern. ; P. subaculeatus, 

 Murch. ; Orthis productoides, Murch. ; a Himalayan fossil, three 

 magnesian limestone species found in the neighbourhood of Sun- 

 derland, and a few doubtful forms, as Productus spinulosus. 



The above shells are found in the Devonian, Carboniferous and 

 Permian deposits. They have equally as extensive a geographical 

 range. M. Verneuil has discovered two species in Russia : three 

 species occur in the magnesian limestone of Sunderland, one of 

 which I have found in the Zechstein of Konitz in Thuringia : 

 one (or more) belongs to our home carboniferous deposits : spe- 

 cies identical with those found in Russia, and some others, occur 

 in the Eifel and the Bas-Boulonnais : and I have specimens of a 

 species % collected by the late Dr. Gerard in crossing the boundary 



* There is a slight but interesting difference between Strophalosia and 

 Productus in their ovarian impressions or crescent-shaped bodies, which will 

 be explained and figured in my " Monograph." 



f This mode of attachment of Strophalosia will probably throw some light 

 on the habit of Productus. Many suppose that the latter was attached by 

 means of fibres passing out between the hinge-plates, which does not appear 

 to be supported by any evidence : Koninck, from an examination of Pro- 

 ductus proboscideus, supposes that it was attached by means of fibres pass- 

 ing out of the anterior opening, which would compel us to conclude that the 

 genus did not belong to the Palliobranchiata. Instead of Productus probos- 

 cideus subserving such an office, I cannot but think that it simply served as 

 a passage for the ingress and egress currents. The tubular form of the an- 

 terior opening is also seen in old individuals of a magnesian limestone Stro- 

 phalosia. As the convex valve of Strophalosia was attached, I am led to 

 believe that the same valve of Productus was the inferior one, as is the case 

 with Pecten dentatus, P. Jacobceus, and others having the byssal sinus or 

 notch in the large valve. 



J This is the shell which Dr. Gerard alludes to in his Journal as resem- 

 bling an oyster (vide Asiatic Researches of the Bengal Society, vol. xviii.). 

 As it does not appear to have been named, I embrace the present opportu- 

 nity of dedicating it to this enterprising traveller, and drawing up a pro- 

 visional specific character for it. 



Strophalosia Gerardi. — External Characters. Form oval ; width greater 



