1 i)G On Cyrtoma, a new genus of Fossil Echinida. 



recent, or fossil state, that by the study and comparison of 

 these with the organic remains of the fossil beach, I might 

 be enabled to arrive at some conclusion as to the condition 

 of animal life at the period of its upheavement, and how far 

 the inhabitants of a sea that had covered the present plains 

 of India corresponded with, or differed from, existing forms. 



It must be evident that if similar investigations are beset 

 with difficulties even in Europe, where national institutions 

 have been for centuries devoted to the collection and illus- 

 tration of natural productions, the task must be almost 

 hopeless in the present state of natural science in India. 

 Nevertheless the subject is one of so much importance to 

 the advancement of geological science, and holds out such 

 powerful inducements to further researches, that I have felt 

 desirous, even in the face of circumstances, to attempt a 

 beginning, particularly as the words in italics are those of 

 Sir John Herschel, expressed with regard to this subject. 

 The difficulty may however be lessened by taking up the 

 subject in parts, and the part we have chosen for this com- 

 munication is not the least interesting or important. 



Before going into the subject of the fossils, a few obser- 

 vations on the general characters and nature of the group 

 of animals to which they belonged, will be necessary. Echi- 

 nida seem to have been very abundant about the period 

 of the chalk formation. Their first appearance is in the 

 Oolitic formation, from this they ascend to the green sand, 

 increasing in number and variety till the period of the chalk, 

 in which we probably find they were more numerous than at 

 any former or even subsequent time; from the chalk forma- 

 tion they are traced upwards through the series of tertiary 

 rocks, some species becoming extinct and others appearing 

 in their place. The structure and habits of such as now 

 live are not yet sufficiently known to enable geologists to 

 elucidate all that it would be desirable regarding extinct 

 species, far less to enable naturalists to make any great 

 advancement towards the natural arrangement of the order. 



