190 



Miscellaneous. 



In order to express the relations of the two subclasses of Crus- 

 tacea, we have published * the following table, showing the mode of 

 grouping of the different orders of the two subclasses of the class 

 of Crustacea : — 



Classification of the Subclasses and Orders of Crustacea. 



<% 



Neocartda. 



to 



o 



. bo 



2 S 



Pai^eocarida. 



I 

 Crustacea. 



"While the Neocarida are characterized by the well-known fea- 

 tures peculiar to all living Crustacea except Limidus, the Palaeo- 

 carida have, among others, the following characters : — Appendages 

 of the cephalothorax in the form of legs rather than jaws ; no an- 

 tennae ; brain on the same plane as the cephalothoracic ganglionic 

 ring, and supplying nerves to the eyes alone ; nerves to the 

 cephalothoracic appendages sent off from an oesophageal ring ; 

 nervous system ensheathed by a ventral system of arteries ; meta- 

 morphosis slight. Sexes distinct. 



Order 1. Merostomata. — No distinct thoracic segments and ap- 

 pendages. (Limidus, Eurypierus, &c.) 



Order 2. Trilobita. — Numerous free thoracic segments and jointed 

 appendages. (Agnostus, Paradoxides, Calymene, Trinucleus, Asa- 

 phus, &c. ; all extinct.) 



A further elaboration of this classification, with full references 

 to the labours of others, is to be given in a second memoir on the 

 anatomy and development of Limidus pohjphemus, in course of 

 preparation. — American Naturalist, December 1879. 



* Zoology for Students and General Readers. American Science 

 Series. By A. S. Packard, Jun. H. Holt & Co., New York. Published 

 in December 1879. 8vo, pp. 703. 



