192 Report of the State Geologist. 



moreover, only in shallow water, mostly in the zone alternately 

 covered and uncovered by the tides. Such are the Pholads, the 

 Teredos, the genera Saxioava^ Venerupis, Zithodomus. But all 

 these forms have representatives in the fossil state; the holes 

 formed by them are frequently met with either with or without 

 the shell in their interior (for example, in the Bathonian of the 

 Ardennes, the Faluns of Pontlevoy, etc.). Their presence is a cer- 

 tain indication of the existence of a littoral zone of a rocky 

 character. This particular facies presents also numerous forms 

 which pertain to it exclusively, as the Patellas, Littorinas, 

 Ealani and various forms of Trochus. 



Oysters, Mussels, Plicatulas, etc., which live attached to the 

 rocks, either directly by one of their valves, or by means of their 

 byssus, are associated with forms which characterize the highest 

 marine zone ; they may, indeed, descend deeper in a zone which 

 is never exposed, and where they are accompanied by the Echini 

 and Brachiopoda. The great majority of deposits of this nature 

 contain animals which have lived fixed, or which crept on the 

 bottom, mixed with the remains of swimming animals which 

 could live in the deep sea and also approach near the coast, and 

 whose shells fall to the ground after death ; such are the 

 Cephalopods. The Nautilids, the Ammonites and the Belemnites 

 are found side by side with the Gasteropoda, the Acephala and 

 the Echini. 



The expression LiUoval fades has then, in Geology, a broad 

 signification, aid is applied to a more extended zone than that 

 which at the present epoch is called the littoral zone. It indi- 

 cates simply that the formation in question was produced in the 

 vicinity of a coast. It may present pelagic elements, but it is 

 characterized by the presence of the littoral elements which we 

 have cited. 



Pelagic facies. — We call pelagic animals those which are 

 adapted by their structure to the function of swimming in the 

 deep sea without resting on the bottom or on the shores. Of 

 this class there are at present the Cetacea, Fishes, Cephalopoda, 

 Pteropoda, Medusae, many Foraminifera and Radiolaria. In many 

 regions deposits of great depths have furnished organized 

 remains of only such as belonged to these groups, and derived 



