34 GEOLOGY OF THE ISLE OF WIGHT 



crosses the bottom of Whale Chine. The Scaphites and 

 Crioceras are Cephalopoda, related to the Ammonites ; 

 but in this Lower Cretaceous period a remarkable develop- 

 ment took place ; many of the shells began to take 

 curious forms, to unwind as it were. Crioceras, a very 

 beautiful shell, has the form of an Ammonite, but the 

 whorls are not in contact ; thus making an open spiral 

 like a ram's horn, whence its name (Gk. x^ar, ram, 

 jtjcjor, horn). Ancyloceras begins like Crioceras, but from 

 the last whorl continues for some length in a straight course, 

 then bends back again ; Macroscaphites is similar, but the 

 whorls of the spiral part are in contact. In Scaphites, a 

 much smaller shell, the uncoiled part is much shorter, 

 and its outline more rounded. It is named from its 

 resemblance to a boat (Gk. o-^a^i;).* 



The Walpen and Ladder Clays and Sands (about 60 ft.) 

 contain nodules with Exogyra and the Ammonite 

 Douvilleiceras martini. The dark-green claj's of the lower 

 part form an undercliff, on to which Ladder Chine opens. 

 The Upper Crioceras Group (46 ft.), like the Lower, con- 

 tains bands of Crioceras? also Douvilleiceras martini, 

 Gervillia, Trigonia, etc. It must be stated that there 

 is some uncertainty with regard to the ammonoids found 

 in this neighbourhood, Macroscaphites having been 

 described as Ancyloceras, and also sometimes as Crioceras. 

 The discovery of the true Ancyloceras (Ancyloceras 

 Matkeronianum) at Atherfield is described (and a figure 

 given) by Dr. Man tell ; but what is the characteristic 

 ammonoid of the " Crioceras " beds requires further 

 investigation. The neighbourhood of Whale and Walpen 

 Chines is of great interest. Ammonites may be found in 

 the bottom of Whale Chine fallen out of the rock. Red 

 ferruginous nodules with Ammonites lie on the shore, 

 in the Chines, and on the Undercliff, some of the am- 

 monites more or less converted into crystalline spar. 

 * See Guide to Fossil Invertebrata, Brit. Mus. Nat. Hist. 



