FIG. 41. CEPHALOPOD COILING CYCLE. 



a, a 



Mcloceras [Cyrloceras] 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^), showing orthocone, cyrtocone, and ophiocone 

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

 Jurassic (Kellaways Rock), (X2); 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 bituberculatum 

 d'Orbigny, Neocomian. Toxpcone. 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. j, Hamites, Albian. A 

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

 after d'Orbigny. All x j, unless otherwise stated. 



