R. ETHERIDGE, JUN., ON A LOWER-CARBONIFEROUS PRODUCTUS. 459 



habits of the Producti, and use of their spines, briefly summed up 

 under those two headings, is as follows : — 



A. Habits. 



That the Producti were regarded as : — 



1. Free shells, by Fleming, Deshayes, De Verneuil (partly), and 

 Chen u. 



2. Living with the ventral or convex valve downwards, by 

 Sedgwick and Murchison, Keyserling and D'Orbigny. 



3. Attached by tendons passing through tubes arranged along the 

 hinge-line, under the general name of Leptcena, by Yon Buch (an 

 opinion afterwards abandonod). 



4. Attached by means of a peduncle passing through a central 

 triangular foramen, by Bouchard-Chantereaux. 



5. Attached by fibres passing between the free edges of the shell, 

 by De Koninck, Geinitz, and Eichwald. 



6. Probabty attached when young, but a few permanently 

 attached, by S. P. Woodward. 



7. Attached by spines (in the case of the allied genus Strophalosia), 

 by King and De Koninck {fide Davidson). 



B. Spines. 



That the spines were considered — 



1. To be for the passage of tendons of attachment, by Yon Buch. 



2. To be for the introduction of water into the interior of the 

 shell, by De Verneuil. 



3. To be for simply retaining the shell in position in fine sedi- 

 ments, by D'Orbigny. 



4. To be without essential function, by Bronn. 



5. To be of unknown function, by Eichwald. 



6. Not to serve as a means of attachment to the shell, by De 

 Koninck and De Verneuil. 



7. Not to act as a conduit to the interior of the shell, by De 

 Koninck and Bronn. 



3. Description of the Specimens. — With the foregoing brief outline 

 of the views of some of the more eminent authorities, I pass on to a 

 description of the specimens. 



We possess specimens of this adherent Productus in four condi- 

 tions : — 1st, attached by the spines of the ventral valve to foreign 

 bodies (figs. 1-5, & 11) ; 2nd, a few detached conjoined ventral and 

 dorsal valves ; 3rd, detached dorsal valves (figs. 18-22) ; and, 4th, 

 fragments of detached ventral valves with the remains of spines 

 (figs. 16, 17). The first and fourth conditions are by far the most 

 common, and with regard to one another in about equal proportions. 

 In size the individuals vary from less than a line in diameter(fig. 13) 

 up to a little more than two lines (fig. 24), and are attached to 

 small Encrinite stems and fragments of Polyzoa, but generally to 



