ZOOLOGICAL AFFINITIES. 9 



have consisted essentially of some chitinous material, impregnated sometimes with 

 a certain amount of lime. In the greater number of species the shell is made up 

 of two distinct layers ; the outer is usually dark-coloured, semi-transparent, and 

 highly ornamented ; the inner is of a paler colour, more opaque, thinner, and nearly 

 smooth (Plate V, fig. 10 h). In such transverse sections as I have been able to 

 obtain this division is not well marked, but the two layers are often clearly seen 

 where the outer is partially flaked off. In some species where the shell is excep- 

 tionally thin it is apparently quite homogeneous. The structure of the shell is 

 best seen in some specimens of G. quadrisulr.ata from the ironstone nodules of the 

 Coal Measures. 



(9) Preservation of the Shell. — The shells are preserved in limestones, sand- 

 stones, shales, slates, and ironstone nodules. They are always liable to compression, 

 the result being in some cases actual contact between the upper and under faces. 

 When the specimens are large they are seldom perfect, the apertural part being 

 broken away more often even than the apical portion. Frequently also only one 

 or two faces are preserved. Sometimes the different layers of the shell are seen 

 in an excellent state of preservation, especially in specimens from the ironstone 

 nodules ; but more often the outer layer is considerably damaged, and along the 

 summits of the ridges the shell may be entirely gone, little isolated portions 

 remaining in the furrows (PI. Ill, fig. 4/;). Lastly, in a large number of cases 

 no shell is preserved, and the fossil is in the form of either an external or an 

 internal cast. 



DISTRIBUTION OF THE GENUS. 



Conularia, though never really common, is found distributed through the 

 British rocks from the Upper Cambrian to the Upper Carboniferous. During 

 this period the maximum development was reached in Middle and Upper Ordo- 

 vician and Silurian times, when twenty-two out of the thirty British species 

 occurred. Above this horizon the number of species diminishes, five appearing in 

 the Carboniferous rocks, only one of which survives in Upper Carboniferous times. 

 Examples arc found in the Budleigh Salterton Pebble Bed, but these are all 

 derived. [See Table on p. 10.] 



ZOOLOGICAL AFFINITIES. 



The position in the animal kingdom in which the genus Conularia should lie 

 placed, has been a subject of contention from the time when Sowerby wrote, in 

 1821, that "it may perhaps belong to that family of Lamarck's order of shelly 

 animals — ' Crassipedes ' — which inhabit tubes, and contains Teredo and some other 

 tubiform shells, whose tubes are sometimes jointed." ] Very soon after this, and 

 1 Sowerby, ' Miu. Couch.,' vol. iii (1821), p. 107. 



2 



