30 GASTEROPODA OF THE INFERIOR OOLITE. 



unfavorable to its development, and partly because the mechanical sediments mask 

 those of organic origin. I have before observed that the horizon may be roughly 

 represented as the zone of Am. radians. The lower portions (not visible in 

 this section) may probably be the equivalents in time of the Jurensis -beds, as 

 identified by Tate and Blake in Yorkshire, whilst the upper portion may be taken 

 to represent the cynocephala-st&ge of Lycett. 



It so happens that in one place a complete section of the Inferior Oolite Lime- 

 stone has slipped to the base of the cliff, and therefore we are fortunately able to 

 effect an examination which would otherwise require a considerable, not to say 

 dangerous, exertion. The following profile, therefore, though measured at the 

 bottom, really represents the top of the cliff. It shows us the Inferior Oolite in a 

 nutshell, and affords a clue to its development in this neighbourhood and to a 

 certain extent throughout the Dorsetshire district. Its modest dimensions seem 

 puny in comparison with the bulky Cotteswolds and the still thicker masses 

 of the Yorkshire Oolites. Nevertheless, though small it is regular in sequence 

 and the life-zones are fairly shown, better perhaps than in any one section 

 of the Inferior Oolite throughout England. Doubtless there are deficiencies, and 

 the Parhinsoni-zone is in preponderating force. 



Profile No. 1, see page 31. — Taking these beds in ascending order and without 

 too detailed a scrutiny, we perceive that above the main mass of " Yeovil Sands " 

 there occur about seven feet of sand-rock and calciferous grits between two lines 

 of very thin, smooth, sharply-keeled Ammonites. These, no doubt, are the beds 

 referred to by Oppel, who says that he found here the beds of Am. torulosus in 

 the form of sandy, light grey limestone charged with numerous organic remains, 

 amongst which he collected Am. torulosus, opalinus, and subinsignis, Turbo sub- 

 duplicatus, Terebratula angllca, and Rhynchonella cynocephala. 1 



Speaking from my own experience the fossils of this horizon are mainly confined 

 to the vicinity of the upper line of Am. opalinus, which Oppel regards possibly as 

 the equivalent of his zone of Trigonia navis. There is here a fossiliferous zone 

 which teems with Am. opalinus, and I possess both the other species of Ammonites 

 mentioned by Oppel from this place and most probably from the same horizon. 

 Bhynch. cynocephala was also noted from here, and likewise a few species of 

 Gasteropoda, but not enough to constitute what the local collectors call a 

 ''Univalve Bed." 



The remainder of the section upwards consists of five blocks of limestone, 

 which measure altogether about twelve feet in height. The most notable shell- 

 bed in the lower portion is one in connection with the " irony nodule " bed, 

 a well-marked physical horizon in this neighbourhood. Ammonites greatly 

 resembling Am. Murchisonee occur hereabouts, and there are a sufficient number of 

 1 See Oppel, ' Juraformation,' p. 328, 1856-58. 



