244 



MR. T. ROBERTS ON THE UPPER JURASSIC ROCKS 



They do nob, however, present the same lithologieal character 

 throughout the district. 



In the ' Combe Grede ' the lower beds of the Corallian are repre- 

 sented by limestones containing JRhynchonella inconstans, Terebra- 

 tula insignis, Cidaris-, &c, and above these come some greyish compact 

 limestones, containing species of Cidaris and Hemicidaris. 



In the debris thrown out from the Loges tunnel, in which the 

 Corallian beds are pierced, the rock pointed out to us as belonging 

 to this horizon is composed of brown and some grey argillaceous 

 limestones, rich in fossils ; the following is a list of the principal 

 ones obtained by us : — 



Turbo Meriani, Gold/. 

 Lima rigida, Sow. 



Kenevieri, Et. {cf. grandis, 



Bom.). 

 Pecten lens, Sow. 

 Ostrea solitaria, Sow. 



Terebratula Bauhini, Et. 

 Pvhynchonella pinguis, Op. 

 Cidaris florigemma, Phil. 

 Stomeckinus perlatus, Ag, 

 Glypticus hieroglyphicus, Ag. 



The Astartian is divided into two substages — an upper, cal- 

 careous, and blower argillaceous one. The general character of the 

 former is thick-bedded homogeneous limestone, although at times 

 it is oolitic. The oolitic portion of these beds is usually fossili- 

 ferous, but the fine-grained limestones rarely contain fossils. The 

 lower or argillaceous division of the Astartian near Locle is 50 

 metres (164 feet) thick, and consists of clays and limestones varying 

 in character and thickness ; the limestone is sometimes oolitic and 

 marly, whilst the clays are at times quite arenaceous. In the 

 upper part of this substage there is a fossiliferous zone with Tere- 

 bratula humeralis : and lower down there is another marly bed con- 

 taining this same fossil in abundance. Both of these fossiliferous 

 marly beds are seen near the summit of Mount Chasseral, and again 

 further north, on the other side of the St. Imier valley. 



On the roadside opposite Brenets the following section in the 

 lower beds of the Astartian was observed : — 



ft. 



5. Well-bedded greyish limestones 12 



4. Marls, with some thin beds of limestone containing Melania 



striata 10 



3. Greyish limestone 20 



2. Alternations of limestone and marls 8 



1. Greyish limestones 5 seen. 



The marls with Terebratula humeralis also occur in the railway- 

 cutting near jSToiraigue. 



In the neighbourhood of Ste. Croix the Astartian is composed of a 

 compact reddish limestone, which is well seen on the roadside to 

 the north-west of that town. 



The following fossils come from the marly beds near the summit 

 of the Chasseral : — 



Ckemnitzia heddingtonensis, Sow 

 Trigonia subconcentrica, Et. 

 Terebratula humeralis, Rom, 



Terebratula suprajurensis, Ag. 

 Cidaris florigemma, Phil. 

 Hemicidaris, sp. 



