CTRTOCEEATID^. 
263 
cian and Silurian species consists for the most part merely of lines 
of growth, sometimes developing into imbricating striae, which are 
generally stronger in the region of the body-chamber. A few Silu- 
rian species are strongly sculptured ; of these the following may be 
cited, viz, : — Cyrtoceras {Meloceras) corhulatum, Barr., in which 
there are longitudinal ridges, crossed by imbricating lamellae ; Cyr- 
toceras {Meloceras) pergratum, Barr., and Cyrtoc. (Aleloceras) extri- 
catum^ Blake, both of which species are furnished with distinct 
Fig, -16. 
Cyrtoceras depressum. — a, front Anew ; h, side view. Reduced to rather less 
than ^ the natural size. From a specimen in the National Collection. 
annulations. Some of the species of Ooceras are also annulated, 
though feebly. These two series of longitudinally ridged and an- 
nulated species may be paralleled with species of Ortlioceras having 
similar ornaments. Some Devonian species, such as Cyrtoceras 
{Mehceras) lamellosum, d’Arch. and de Yern., are conspicuously 
ornamented, as are also some of the Carboniferous species, such as, 
e. g., Cyrtoceras {Meloceras) canaliculatum, de Kon., &c. Colour- 
hands are seen in some speciesh 
Cyrtoceras ranges from the Cambrian to the Carboniferous, the 
greater number of forms being found in the Silurian. 
^ See, e. g., Cyrtoceras depressum, Goldfuss. Barrande describes and figures 
several species of Cyrtoceras which have bands of dark or light colour upon 
their shells. See Syst. Sil. de la Boheme, 1867, vol. ii. pt. i. p. 433. 
