34 GEOLOGICAL MEMOIRS. 



Eritomozoa. 



Vermes 288 



Crustacea 894 



JMyriapoda 17 



Arachnoidea , 131 



Hexapoda 1551 



2881 



Spondylozoa. 



Pisces 1318 



Reptilia 384 



Aves 148 



Mammalia 705 



2555 



Animalium summa 24,008 



The total number of fossil species enumerated in this portion of 

 the treatise therefore amounts to 26,678. In the continuation of the 

 work, the author intends to present the general geological and zoolo- 

 gical conclusions derived from this view of the periods at which the 

 various races of organic beings first appeared on the globe. [J. N.] 



Notes on Trilobites. By M. Barrande. 



[From Haidinger's Berichte von Freuiiden der Natur, in Wien, vol. iv. p. 353.] 



Whilst investigating the Bohemian trilobites, M. Barrande has 

 come to the conclusion that no good classification of this family has 

 yet been proposed. The division according to the peculiarities of 

 the eyes, as wrought out by Goldfuss, Quenstedt and others, though 

 based on an important character, is yet too artificial, and has too 

 little regard to the diversity of other organs. Burmeister has selected 

 the capability of rolling themselves up, as the basis of his highest 

 divisions ; but M. Barrande by careful search has succeeded in find- 

 ing individuals of all species of trilobites, even those said not to 

 possess this power, rolled up, and consequently this distinction fails. 

 The classification in Corda's work on the Bohemian trilobites is 

 founded on a character of small importance in regard to the entire 

 organization of the animal, namely on the peculiarity of the caudal 

 plate {Pygidium) as either entire or divided on the margin. By this 

 classification, species of one and the same genus are placed in two 

 distinct sections of the family ; as for example, Phacops stellifer is 

 distinguished by no character, except the divisions of the tail, from 

 the other species of Phacops in which it is entire on the margin. M. 

 Barrande thinks that a good classification, on which M. L. von Buch 

 is said to be at present engaged, will only be possible when a greater 

 number of species are known ; and recommends special research to 

 be made for them in localities where they abound. 



The largest Bohemian species known to him is the Paradoxides 

 Linnei, which attained a foot in length. One of the largest species 

 is the Asaphus nobilisy which is also remarkable for the sculpturing of 

 its shell. 



An interesting peculiarity of many species of Odontopleuray par- 

 ticularly 0. Buchii and Keyserlingii, is that some individuals are 



