146 Dr. W. T. Caiman on the 



Euphausiidap, with wliicli they had until then been associated. 

 Boas divided the Malacostraca into seven orders — the Euphau- 

 siacea, Mysidacea, Cumacea, Isopoda, Aniphipoda, Decapoda, 

 and Squillacea. This view was severely criticised byClaus*, 

 who, while admitting points of affinity between Mysidas and 

 A rthrostraca on the one hand, and between Euphausiidaa and 

 Decapoda on the other, retained the Schizopoda as a central 

 and primitive group, and classed them along with the 

 Decapoda as Thoracostraca. 



In 1893 Dr. Hansen f, in a preliminary account of his 

 researches on the morphology of the appendages in Injects 

 and Crustacea (not yet published in full), proposed a still 

 further modification of the classification on the lines laid down 

 by Boas, from whom, however, he differs on many points. 

 While agreeing in discarding the group Schizopoda, Hansen 

 points out that the Euphausiacea do not occupy the primitive 

 position assigned to them by Boas, and he emphasizes their 

 close affinity with the Decapoda, with which he proposes to 

 associate them, opposing to the group thus formed another of 

 equal rank, comprising the Mysidacea, the Cumacea, and 

 the Edriophthalmate orders. Hansen's proposals seem to 

 have attracted little attention, and I am not aware that any 

 writer has adopted the classification suggested, though to me 

 this arrangement of the Malacostraca appears to be the only 

 one which adequately expresses our present knowledge of 

 their morphology. 



As Dr. Hansen does not give any names to the two groups 

 which he defines, it may be convenient to state here that I 

 propose the names PERACARIDA (Trrjpa, a pouch) for the 

 division which includes the Mysidacea, Cumacea, Tanaidacea, 

 Isopoda, and Aniphipoda, and Eucarida for the Euphausi- 

 acea and Decapoda. 



From this it will be seen that the chief point on which 

 there is divergence of opinion is the retention of the Schizopoda 

 as a natural group. That the Mvsidas present affinities with 

 the Edriophthalma and the Euphausiidap with the Decapoda 

 is not disputed ; but if we adopt Claus's view that the 

 Schizopoda are a central group approximating to the stock 

 from which the other ordeis have been derived, there is 

 nothing to forbid their association with the other Podo- 

 phthalma in our taxonomic arrangement. When, however, 



* " Neue Beitrage zur Morphologie der Crustaceen," Arb. Zool. Inst. 

 AYien, vi. pp. 1 -108, pis. i.-vii. (1885). 



t " Zur Morphologie der Gliedinassen und Mundtheile bei Crustaceen 

 und Insecten." - Zool. Anz. xvi. pp. 193-198 & 201-232. Translated in 

 Ann. & Mag. Nat. Hist. (6) xii. pp. 417-434 (1893). 



