1870.] GEOLOGY AND MINERALOGY. 225 



and character of the eyes and ocelli, confirm this view. The 

 organization and the habits of Limulus throw much light on the 

 probable anatomy and habits of the trilobites. The correspond- 

 ence in the cardiac region of the two groups shows that their 

 heart and circulation was similar. The position of the eyes shows 

 that the trilobites probably had long and slender optic nerves, 

 and indicate a general similarity in the nervous system. The 

 genital organs of the trilobites were probably very similar to 

 those of Limulus, as they could not have united sexually, and the 

 eggs were probably laid in the sand or mud, and impregnated by 

 the sperm cells of the male, floating free in the water. 



The muscular system of the trilobites, must have been highly 

 organized as in Limulus, as like the latter they probably lived by 

 burrowing in the mud and sand, using the shovel-like expanse of 

 the cephalic shield in digging in the shallow palaeozoic waters after 

 worms and stationary soft bodied invertebrates, so that we may 

 be warranted in supposing that the alimentary canal was con- 

 structed on the type of that of Limulus, with its large, powerful 

 gizzard and immense liver. 



Cope's Synopsis of the Extinct Batrachia and Kep- 

 TILIA OF America. — The second part of this admirable mono- 

 graph has appeared, and includes the known species of fossil 

 Birds, in addition to the reptiles. It affords an invaluable guide 

 to the student of American Fossil Beptilia, and places for the 

 first time before those who have been engaged in this study, a 

 conspectus of what is known, with the addition of many new 

 discoveries, and profound general observations of the author, who 

 has long been engaged in studies of this kind, more especially in 

 New Jersey and Pennsylvania, and has made himself completely 

 master of his subject. Prof. Cope thus states in his preface his 

 aims and results: — 



" It is not designed in the present essay to give descriptions of 

 the known remains of the Batrachia, Beptiles and Birds, which 

 have been more or less fully made known by others. This is left 

 for the day when our knowledge shall more nearly approach 

 completeness. While the subject is in its infancy, I have thought 

 best to describe only those species and types which are new, and 

 those portions of imperfectly known forms which will throw 

 additional light on their relations and affinities. In adhering to 

 this plan, I have been able to add no little to the history of the 



