BIHANG TILL K. SV. VET.-AKAD. HANDL. BAND 10. N:0 14. 13 



description. He then regarded it as belonging to the genus 

 Hyperia, H. cornigera. The only characters meutioned by him 

 on this first occasion were : »the upper antennas about as long 

 as the body, and the fifth or sixth pair of legs the longest». 

 When in 1840 he institutes a new genus for the animal in 

 question, he gives a very good diagnosis, generic as well as 

 specific, but none of the låter authors has been able to recog- 

 nise it, and Tyro has had the same fäte as Lanceola, being 

 thrown from one place to another in the system. Dana ^) 

 placed it next to Lestrigomis, MiLNE-EDWAEDS,totally overlooking 

 the statement of Milne-Edwårds as to its difference from the 

 true Hyperise »tete tronquée anterieurement». But that was 

 not his only fault, for in the same volume -) he gives an 

 accurate description of some animals, certainly belonging to 

 the genus Tyro, under the new generic name Clydonia ^). 

 This new genus he placed in the family Corophidae as the type 

 of a subfamily of its own, Clydonina;, and established two 

 species, C. longipes from the Pacific and C. gracilis from the 

 Atlantic. C. Spence Bate followed him and classified Tyro 

 among the Hyperidae and Clydonia among the Corophidae *). 

 To make the identity of the two genera more apparent, 

 I here reläte the principal points of the original descriptions 

 arranged side by side: 



Tiiro. H. Milne-Edwaeds. 

 The head truncated anteriorly. 



Body Hyperia-like. 



The upper antennas are straight, 

 long, longer than the body, two- 

 jointed, the basal joint short, the 

 terminal long, stout, tapering. 



None of the legs prehensile; they 

 are unequal in length, 



the fifth pair are much longer than 

 the others. 



Clydonia. Dana. 



The head is short about half as 

 long as wide. 



Body elongate, somewhat de- 

 pressed. 



The antennse are straight, rigid, 

 long, about as long as the body, 

 two-jointed, basal joint short, the 

 terminal long, rigid, subulate (extre- 

 mity obsoletely multiarticulate). 



Feet slender, the four anterior 

 shortest, and have no proper hands; 

 the six posterior are long, filiform* 

 the fifth pair are the longest. 



^) sUnited States Expl. Esp., Crustacea-^. Vol. 2. 1853. Pag. 980 and 1482. 



=^) 1. c. pag. 83i. 



^) Previously published in the year 1850 in >Proceedings of the American 



Academy of Arts and Sciences?. Vol. 2. Pag. 219. 

 ■•) »Catal. of the spec. of Amph. Orust, in the Coll. of the Brit. Museum». 



Pag. 284 and 308. 



