INVEBTEBRATA, CRYPTOQAMIA, MICROSCOPY, ETC. 713 



give an account of the genera states that he has not seen the works of 

 Hodge, and docs not know whether he gives any diagnosis of the 

 genus. The writer of this notice has made it his business to refer to 

 the ' Trans, of the Tyneside Nat. Field Club,' in which Mr. Hodge's 

 paper appeared, and finds that, after the notice of the species, the 

 writer says that from the " peculiar character of the rostrum, absence 

 of true palpi, and number of eyes, it would appear to form the type 

 of a new genus," without any more definite diagnosis. The paper 

 concludes with a short account of a new genus Cnjptognathus, and of 

 the species lagena ; it is illustrated by a plate of fifteen figures. 



The Nebaliad Crustacea as Types of a New Order.* — The 



Nehaliadce, represented by the existing genus Nehalia, have generally 

 been considered to form a family of Phyllopod Crustacea. Metschni- 

 koff, who studied the embryology of Nehalia, considered it to be a 

 " Phyllopodiform Decapod." Besides the resemblance to the Deca- 

 pods, there is also a combination of Copepod and Phyllopod character- 

 istics. The type is an instance of a generalized one, and is of high anti- 

 quity, having been ushered in during the earliest Silurian period, when 

 there were, when we regard the relative size of most Crustacea, and 

 especially of living Nehalice, gigantic forms. Such were Ditliyrocaris, 

 which must have been over a foot long, the carapace being seven 

 inches long. The modern Nehalia is small, about half an inch in 

 length, with the body compressed, the carapace bivalved as in Lim- 

 nadia, one of the genuine Phyllopods. There is a large rostrum 

 overhanging the head, stalked eyes, and besides two pairs of autennfe 

 and mouth parts, eight parts of leaf-like, short, respiratory feet, 

 which arc succeeded by swimming feet. There is no metamorphosis, 

 development being direct. 



Of the fossil forms, Hymenocaris was regarded by Salter as " the 

 more generalized type." The genera Peltocaris and Discinocaris 

 characterize the lower Siliu'ian period, Ceratiocaris the uj^per, Dic- 

 tyocaris the ujiper Silurian and the lowest Devonian strata, Ditliy- 

 rocaris and Argus the Carboniferous period. Our existing north- 

 eastern species is Nehalia hipes (Fabricius) which occurs from Maine 

 to Greenland. 



The Nebaliads were the forerunners of the Decapoda, and form, 

 we believe, the type of a distinct order of Crustacea, for which the 

 name Phyllocarida is proposed. 



Physiology of the Nervous System of the Crayfish, t— Mr. James 

 Ward, M.A., gives a brief account of ex2)criments, consisting mainly 

 in severing (1) one or (2) both of the supra-cesophageal commissures, 

 (3) both the sub oesopliageal commissures, or (4) in dividing the 

 supra-oesophageal ganglia longitudinally. 



From these experiments it may perhaps, with more or less proba- 

 bility, be inferred that : — 



(rt) There is no decussation of the longitudinal fibres in the 

 nervous system of the crayfish. 



* ' Am. Nat.,' vol. xiii. (1879) p. 128. 

 t ' Proc. Eoy. Soc.,' xxviii. (1879) p. 379. 



