266 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 4, 



thium subcostellatum, a small Cytherea, Ci/rena semistriata, and a 

 Natica. 



b. The upper Hempstead freshwater and estuary marls and carbo- 

 naceous clays. — Cerithium plicatum, accompanied by C. elegans and 

 tricinctum 1, abounds in the brackish water portion of these beds, 

 and Paludina lenta, along with species of Limneus, Planorbis, and 

 Uriio, in the freshwater strata. They pass below into unfossiliferous 

 variegated marls. 



c. The middle Hempstead freshwater and estuary marls. — These 

 are distinguished by the presence of vast numbers oi Melaniafasciata, 

 and alternate with beds filled vdth Paludina lenta, and cypridiferous 

 clays. Seed-vessels are also very abundant. These beds likewise 

 pass below into variegated marls. The lowest bed is a brackish water' 

 band of Cyrena semistriata, mingled with peculiar Cerithia and a 

 remarkable Panopcea. 



d. The lower Hempstead freshwater and estuary marls. — These 

 are distinguished by the presence of Melania muricata and a peculiar 

 Melanopsis, a new Modiola, peculiar small univalves, cyprides, and 

 plant remains. Its lowest bed is a strong carbonaceous stratum, 

 3 feet thick, to which I have applied the name of " Black band." 

 It is in this bed that the Rissoa Chastelii commences to appear. 



The seed-vessels oiChara medicagimda and C. helicteres, not those 

 so-called in British papers, but the true Brongniartian species, cha- 

 racterize the Hempstead series. The superficial area occupied by 

 this division is very small. 



B. The Bembridge Series. (Figs. 1 & 3, 6, c.) 



The beds of this division attain a thickness of more than 100 feet. 

 They are widely spread and well-preserved. They consist of marls, 

 clays, and limestones of freshwater, brackish, and marine origin. 

 Cyrena semistriata, var. antiquior, ranges through the beds, but is 

 not found lower down. Paludina lenta, Melania muricata, and 

 Melanopsis carinata are also vddely and abundantly distributed 

 through them. This section may be subdivided as follows : — 



a. Upper Bembridge marls, distinguished by the abundance of 

 Melania turritissima, n. s. 



b. Lower Bembridge marls, characterized by the abundance of a 

 Cerithium, possibly a variety of C. mutabile, Cyrena pulchra, Cyrena 

 obovata, var., and Cyrena obtusa, n. s. Remains of Trionyoc are 

 frequent in these beds. 



c. Bembridge oyster-beds. — Green marls and sandy bands, in many 

 places abounding with Ostrea, sp. ?, accompanied by peculiar Ceri- 

 thia, Mytili, an Area, a Nueula, &c. ; the univalves mostly in the 

 condition of casts. 



d. Bembridge limestones. — Compact cream-coloured limestones 

 alternating with shales and marls. Land-shells (most of them de- 

 scribed by Mr. Edwards) are common in this limestone in all places, 

 but are especially abundant at Sconce. The Bulimus ellipticus is 

 one of its most generally distributed and best-known testacea. One 

 of the bands, and a very constant one, is filled with a little globular 



