588 MESSES. GABDNER, KEEPING, AND MONCKTON ON THE 



in a more or less perfect state. Psammohia occurs in it in the posi- 

 tion assumed by the shell when living, and OjjJiiura is met with, 

 but not very commonly. Among the species that do not ascend 

 beyond this horizon are Gassidaria ambigua and Fusus errans. 



The Highcliff or Lower Barton Series closes with a dark drab sandy 

 clay, mottled with glauconitic sand*, 4 feet thick, which weathers a 

 rusty colour. It was tenanted when forming by numerous Phola- 

 domyce, and includes many dead shells of Cytherea elegans. The 

 actual line of separation between it and the Middle Barton is drawn 

 at a dotted layer of large, round, dark- coloured Septaria, which 

 become more dispersed in proceeding westf. 



Except in the terrace and the green clays at the base, the beds 

 usually maintain an angle of about 35°. The fauna of this division 

 of the Barton Series is very rich, numbering between 300 and 400, 

 and, possibly, a considerably greater number of species. For those 

 peculiar to it we have to search among the more minute shells of 

 the Highcliff sands, foremost among them being the well-marked 

 Stromhus bartonensis and Buccinum canaliculatum, Acera striatella, 

 Volvaria acutiuscula, &c. Cassis ambigua is confined to it in the 

 Barton Beds, but reappears in the Middle Headon. We may also 

 mention ScMzaster d^Urbani and the Ojjhiura as characteristic species. 

 There is a host of species which come up from the Upper Brackle- 

 sham, but do not pass beyond the upper limits of the Lower Barton, 

 among such being the typical Terebellum fusiforme, Fusus errans, 

 F. interruptus, Cerithium angidatum, Nucula lissa, Cytlierea elegans, 

 Nummulites elegans, &c. These species, taken together, are suffi- 

 ciently abundant to furnish in the field an undeniable index as to 

 the division of the Bartons we are in. 



The Middle Bakton, or Barton Clay proper. 



Within 5 feet of the Septaria-band last mentioned, and taken as 

 the base of the Middle Barton, a second and more strongly marked 

 one occurs, the Septaria being equally dark in colour, and round 

 and massive in appearance. Both bands are fossiliferous. Though 



* Mr. Grenville Cole describes the sand as fairly rounded, the grains con- 

 taining liquid-enclosures with moving bubbles. The dark green grains are very 

 numerous, and there are also agglutinated sand-grains. The clay effervesces 

 somev^hat in cold acid. 



t The section of the Highcliff Beds, according to Prestwich, Quart, Journ. 

 Geol. Soc. vol. xiii. (1857) p. 108, is as follows : — 



ft. 

 Grey clay with seams of yellow sands and shells ... 20 



Grey sandy clay, with Echini, Gassidaria, &c 50 



Mixed clay and green sands, impressions of shells . 14 

 Bed of flint pebbles in sand, size moderate 1 



85 



Dr. Wright omits the two lowest of these beds from the Barton Series, and 

 gives the remainder a slightly greater thickness (8 feet more), distinguishing them 

 as beds 22, 23, 24 (Proc. Cotteswold Naturalists' Club, vol. i. pp. 129-133, 1853). 

 Our first measurement came to 64, and our second to 59 feet, after accurately 

 reducing them to the vertical. 



