592 



S. S. BTTCKMAN ON" AMMONITES FROM 



The zone of Stephanoceras Humphriesianum contains :- 



Stephanoceras Humphriesianum (Sow.). 

 Harpoceras cycloides (cV Orb.). 

 Cosmoceras subfurcatum (Schloth.). 



Grarantianum (d'Orb.). 



Haploceras oolithicum (cV Orb.). 

 Harpoceras Edwardianum (d'Orb.). 

 Lytoceras Eudesianuin (d'Orb.). 

 Stephanoceras Blagdeni (Sow.). 

 Stephanoceras Braikenridgii (Sow.). 



linguiferum (d'Orb.). 



Sphseroceras Brongniarti (Sow.). 

 Gervillii (Sow.). 



Stephanoceras Deslongschampsii 



(Defrance). 

 Cosmoceras Caumontii (d'Orb.). 

 Sphseroceras Wrightii, 5. S. Buckm. 

 Oppelia subcostata, J. BucJcman. 

 Ammonites cadomensis, Defrance. 

 Perisphinctes Davidsoni, S. S. Buckm. 

 Terebratula spharoidalis, Sow., 



abundant. 

 Astarte obliqua, Desk. 

 Rhynchonella senticosa, von Buck. 

 Terebratula Buckmani, Dav. 



This Humphriesianum zone is the " Fossil Bed " in quarries round 

 Sherborne, where it is so well developed. It has been put down 

 as the equivalent of the Soiverbyi zone or " Fossil Bed " (misleading 

 term) of Bradford Abbas and neighbourhood under the name of 

 " the Cephalopoda bed of the Inferior Oolite ;" and the extraordinary 

 difference in the species has been attributed to the difference in the 

 locality. 



The fact is that the Humphriesianum zone is almost absent 

 at Bradford Abbas, but is represented near Halfway House by a 

 thin band of ironstone, about 6 inches in thickness, which overlies 

 the Soiverbyi zone, and which contains a list of species which agrees 

 with those from the Humphriesianum zone at Sherborne ; while the 

 Soiverbyi zone at Sherborne is often not quarried, and therefore has 

 escaped notice, as it was supposed the quarrymen had reached 

 the sands, as they do at Bradford Abbas. The term " fossil 

 bed," too, was probably answerable for part of the confusion, and 

 shows the necessity for calling beds by the name of some character- 

 istic fossil, and not by some local appellation which may often denote 

 beds at entirely different horizons. 



The zone of Cosmoceras ParJcinsoni contains : — 

 •)• 



Cosmoceras Parkinsoni 



Grarantianum (d'Orb.). 



Oppelia Truellii (d'Orb.). 



subradiata (Sow.). 



Sphseroceras polymorphum (d'Orb.). 



dimorphum (d'Orb.). 



Perisphinctes Martinsii (d'Orb.). 



Stephanoceras zigzag (d'Orb.). 

 Terebratula Phillipsi, Morris. 



sphasroidalis, Sow. 



Stephani, Dav. 



Rhynchonella spinosa (Schloth.). 

 Terebratula globata, Sow., variety? 



Besides the Ammonites here mentioned from these four zones, I 

 have separated about 50 more species, which, so far as I am aware, 

 have not yet been described. These rocks are also well stocked 

 with Gasteropoda, of which there are about 150 different species ; 

 and Lamellibranchiata are very abundant ; of Brachiopoda we have 

 about 40 species made out. 



It may be as well before describing the species to explain a few 

 terms made use of in these descriptions. 



The Inner portion of ivhorl is that which is nearest to the centre 

 of the Ammonite, otherwise called the dorsal part. 



