EXPLANATION OF PLATE 2. A. 



1 STEGANODYCTIUMt CORNUBICUM (M'Coy). Elongate specimen, natural size, shewing the reticular 



structure in parts, from the Devonian slialcs near Polperro. 



2 Portion of Onchus-like mesial stem, natural size, shewing the crenulated longitudinal ridges of the surface, 



with some of the cellular structure at base. 



2 .( Portion of do. highly magnified, shewing the superficial ridges slightly abraded in one comer, and 



the gradual passage of the very small elongated cells near the surface into the larger ones of the centre. 



3 Portion of thin lateral frond, with superficial ridging on the upper part, and the cellular tissue of the 



thickness of the frond exposed below. 



3 a Two of the superficial ridges magnified to shew the openings of the cell mouths. 



4 STEGANODYCTIUM CARTERI (M'Coy). Portion of frond, natural size, shewing the superficial tubercn- 



lation. 



4 a Magnified, shewing the openings of the cell mouths between the tubercles of the surface, and portion of the 



internal cellular structure. 



5 STREPHODES GRACILIS (M'Coy). Natural size, from the Devonian limestone of Plymouth. See page 72. 

 5 a Longitudinal section. 



5 h Horizontal section. 



6 UNCITES L^VIS (M'Coy). From the Devonian limestone of Newton Bushel. 

 6 a Profile of do. 



6 b Section of both valves, at about one third the length from the beak, shewing the thickness of the shell, 



and absence of internal apophyses. 



6 c Section of beak of receiving valve, shewing the great thickness of the shell reducing the inner cavity, and 



absence of internal septa. 



7 STROPHOMENA GIGAS (M'Coy). Natural size, of average specimen, from the Devonian shales of Looe, 



Cornwall ; the lower portion netted by a species of Vioa. 



8 STROPHOMENA NOBILIS (M'Coy). Natural size, from the Devonian limestone of Teignmouth. 



8 a Portion of surface of do. magnified, shewing the longitudinal striation of the surface, and the lines of 



punctures where the shell is decorticated. 



9 ORTHIS PER-SARMENTOSA (M'Coy). From the Devonian shales of Polruan, Cornwall, natural size of 



a specimen shortened by crushing. 



10 PRODUCTA PR^LONGA (Sow.) Natural size, from the sandstone of Croyde: the upper portion is the 



specimen originally figured by Sowerby, the lower portion shewing the mesial ridge as in the Prodiicia 

 C/iristiani of (Kon), belongs to the same individual. 



10* LEPTODOMUS CONSTRICTUS (M'^Coy). Natural size, right valve, from the sandstone of Marwood, N. 

 Devon. 



11 CLYMENIA PATTISONI (M'Coy). From the limestone of S. Petherwin, Cornwall, natural size. 

 11 n View of mouth, shewing the siphon at inner edge. 



11 h Line of septum. 



12 CLYMENIA MUENSTERI (M'Coy). Natural size, from the limestone of S. Petherwin, Cornwall. 

 12 a — — Profile of mouth, and portion of periphery of penultimate wliorl. 



12 b Line of septum. • 



13 CLYMENIA QUADRIFERA (M'Coy). Natural size, from the limestone of S. Petherwin, Cornwall. 

 13 a Line of septum. 



13 'y Portion of periphery. 



14 CYRTOCERAS SUBORNATUM (M'Coy). Natural size, side view, shewing the three rows of tubercles on 



the sides and the convexity of the septum at smaller end, from tlie Devonian limestone of Plymouth. • 



14 rt End view of septum shewing the position of siphon at the outer margin. 



"t" As no Anwrphozoa are described in this Volume the reader is referred for descriptions of the two species of Steganodictyum, to 

 the Annals of Natural History, 2nd Series, Vol. VIII. 



