366 



so brought before the observer, at the frontier of Middle and 

 Upper Lias, has led Continental authors to have recourse to the 

 expedient of binomial naming, a practice claiming but slight 

 advantage, and attended with many drawbacks. Another 

 Ammonite, tolerably common in the Spinatus Zone, existing 

 chiefly in casts and impressions, is Lytoceras lineatum, a difierent 

 shell altogether from Lytoceras jimhriatum, with which some 

 have confused it. The latter is found with us, distinct enough, 

 and quite toward the basement of the Middle Lias. Further 

 notes on the Ammonites are given in part VI. 



When we come to deal with the Dibranchiate Cephalopods, 



we of course in a Uttoral deposit, expect to find them in strong 



force. The Belemnites have been engulfed by shoals at a time 



in these sands when agitated by devious currents, and have left 



their innumerable osselets to testify their former existence. 



Unlike the gasteropods that glided about the surfaces of the 



sea-fronds, these examples are of considerable size as to 



length and thickness, the remains of sea-going adult individuals 



that perished in a storm drift of quicksand. Were time 



devoted to tlie large collection that could be made of these 



fossils, many more species might be made out. It will suffice 



for our purpose to select a few only of the better known, 



principally those described in Prof. Phillips's monograph on 



the British Belemnitidce (Pal. Soc. 1865). One specimen collected 



here is unlike anything figured or mentioned in this work ; but 



we will not yield to the vanity of basing a new name on a single 



specimen. In the opposite degree as concerns number, we 



cite Belemnites paxillosus in its numerous varieties. These 



fosssils swarm throughout the sands. B. paxillosus was named 



B. piger by that old worthy. Dr. Lister, on account of its dark 



colour. Here also we have collected the species Belemnites 



opalinus, Quenstedt — so designated from the opalescent milky 



colour of the conotheca and guard. These names are curious ; 



the older palseontologists were not unlike the earliest navigators, 



who ventured not out of sight of land; all theu' marks of 



distinction were drawn from colour or lithology. The short 



thick forms like B. hreviformis, and P. brevis, are frequently 



