ANIMALS. 95 



Strophalosia and Productus in their ovarian impressions or crescent-shaped bodies ;"^ 

 though nothing has yet occurred to me appearing to mihtate against this conclusion. By 

 referring to PI. XII, figs. 2, 5, 9, 14, and 30, it will be seen, that in StrojjJialosia the 

 vein-like line forming the reniform impressions {e, fig. 5, PI. XII) does not return to 

 nearly the muscular scars, as in Proc^wc/^^^ (vide PL XI, fig. 10/), but to the anterior part 

 of the median plate. Further, there is in the former a vein-like line (/, fig. 5, PL XII), 

 connecting the reniform impressions with the medio-cardinal region of the shell, and 

 which I have hitherto failed in discovering in any true Productus. I do not place much 

 importance on the latter character ; but I am certainly disposed to regard the former 

 one as constituting a part of the generic diagnosis of Strophalosia. A further 

 acquaintance with the internal structure of a number of species, however, is necessary 

 before coming to any positive conclusion on this point. 



I have represented a specimen of StropJialosia parva, which has evidently adhered, in 

 the living state, to the inside of a Froductus Jiorridiis, by means of its umbone {a, fig. 33, 

 PL XII), and numerous long creeping spines belonging -to the same part, as is the 

 ase with some genera of the present day, especially Spondylus. I have now seen so 

 many specimens in this state — that is, with the umbonal spines following the exact 

 concave curvature of the inside of the valve to which they adhered, and with the 

 umbone always impressed, that no doubt remains on my mind of this being their mode 

 of attachment : and from observing in all the Strophalosias with which I am acquainted, 

 the umbone, more or less pressed in and distorted, I am led to believe, that this 

 mode of attachment prevailed, at least in the young state, pretty generally throughout 

 the genus.^ 



The data suggestive of this conclusion are of importance in another point of view, 

 as they go far to disprove the view advanced by Dr. de Koninck, that Productus 

 was attached by means of fibres, or a byssus passing out from between the anterior 

 gape of the valves : no evidences are advanced in support of this view ; and in their 

 absence I am certainly more disposed to conclude from what has just been observed 

 that these shells rested on their large valve, as is the case with Pecten Jacobeus ; and 

 were either free (as perhaps was the habit of Productus giganteui), or firmly moored by 

 means of the cardinal spines to foreign bodies, as may be surmised of Productus 

 horridus. 



The present genus does not appear to have been in existence during any portion of 

 the Silurian period ; but the occurrence of such species as Strophalosia ( Orthis) produc- 

 toides, Murchison, and 8. [Productus) subacideatus, Murch., prove it to have formed a 

 portion of the fauna characteristic of the Devonian system ; while S. {Productus) 



1 Vide Annals and Magazine of Natural History, vol. xviii, p. 93. 



2 M. de Verneuil arrived at the same conclusion with the Strophalosia {Productus) horrescens, which 

 is also furnished with a blunted umbone. (Vide Geol. Russ., vol. ii, pp. 280-1.) 



