FIG. 41. CEPHALOPOD COILING CYCLE. 



a', Meloceras [Cyrtoceras] elongatum Barrande, Silurian. (X^.) 

 Cyrtocone : a, side view, striate ornament indicated at one place, 

 part of test removed, showing suture-lines and part of siphuncle (s) \ 

 a', cross-section, b, Inner whorls of Agoniatites fecundus (Barrande), 

 Middle Devonian (x 3), showing orthocone, cyrtocone, and ophiocone 

 stages ; P, protoconch. c , Spiroceras calloviense (Morris), Upper 

 Jurassic (Kellaways Rock), ( X 2) ; c', initial part (Xio); P, proto- 

 conch. This shows uncoiling from serpenticone to criocone. d, Mor- 

 phoceras dimorphum (d'Orbigny), Bajocian. Ornament omitted. 

 Shows uncoiling, sphserocene to serpenticone ; also five constrictions. 

 e, Turrilites bechei Sharpe, Cenomanian. Ornament omitted except on 

 last whorl, and one suture-line indicated. /, Toxoceras bituberculalum 

 d'Orbigny, Neocomian. Toxocone. g, Scaphites cequalis J. Sowerby, 

 Cenomanian. Scaphiticone, beginning as sphaerocone and ending 

 in a hook, h, Ancyloceras pulcherrimum d'Orbigny, Barremian. 

 Criocone changing to toxocone, with hook-like end. Ornament 

 omitted except near aperture, i, Macroscaphites ivani (Puzos), 

 Barremian. (Xj.) Serpenticone uncoiling, with hook-like end. Orna- 

 ment omitted except on body chamber. /, Hamites, Albian. A 

 generalized figure, a, b, c, After Barrande ; e, after Sharpe ; the rest 

 after d'Orbigny. All X , unless otherwise stated. 



