ANIMALS. 95 
Strophalosia and Productus m their ovarian impressions or crescent-shaped bodies ;”" 
though nothing has yet occurred to me appearing to militate against this conclusion. By 
referring to Pl. XII, figs. 2, 5, 9, 14, and 30, it will be seen, that in Strophalosia the 
vein-like line forming the reniform impressions (e, fig. 5, Pl. XII) does not return to 
nearly the muscular scars, as in Productus (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. XID, 
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 Strophalosia parva, which has evidently adhered, in 
the living state, to the inside of a Producius horridus, by means of its umbone (4, fig. 33, 
Pl. XII), and numerous long creeping spines belonging to the same part, as is the 
case 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 giganteus), or firmly moored by 
means of the cardinal spmes 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) subaculeatus, Murch., prove it to have formed a 
portion of the fauna characteristic of the Devonian system; while S. (Productus) 
! 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.) 
