424 A HISTORY OP EECENT CRUSTACEA 



genus by Latreille, and points out tbat the figures of tlie 

 type-species, Tylos Latreillii^ Audouin, in Savigny's Plate, 

 show the generic characters. Latreille in his ' Families 

 naturelles du Regne Animal,' p. 567, 1825, merely says, 

 ' Ajoutez immediatement apres le genre lygie, Tylos 

 (nouveau genre compose d'especes marines),' so that the 

 information he offers is incorrect. Thus Savigny gave no 

 name ; Latreille gave a name, but did not effectively 

 publish it ; Audouin published the name, with a descrip- 

 tion ; the genus must therefore belong to him. But there 

 is still a difficulty. In 1826 the name Tylos was given 

 by Van Heyden to a genus of Arachnida, and Budde-Lund 

 assigns Audouin's 'Explication' to 1827. M. Eugene 

 Simon, however, has explained that Van Heyden's pro- 

 dromus on the classification of the Acari merely named 

 without defining the genus, and therefore did not effectively 

 pre-occupy the name Tylos. But Audouin's preface is dated 

 1825, and it seems possible, therefore, that the Crustacean 

 genus was really published in advance of the Arachnid. 

 M. Simon, on the contrary, says that the name Tylos 

 armadillo^ Latreille, 1829, was published before the Tylos 

 Latreillii of Audouin's ' Explication,' which can scarcely 

 be correct. Budde-Lund describes, besides the typical 

 Mediterranean species, six others, including two made 

 known by Krauss from South Africa. Tijlos spinulosus^ 

 Dana, is mentioned, and Tylos gramdatus, Miers, from 

 Japan, is distinguished from Krauss's African species of 

 the same name, as Tylos granidiferus. 



Family 3. — Helleriidce, 



The pera3on is as in the preceding family. The pleon 

 has the first five segments fused, with two pairs of short 

 lateral sutures marking off the third from the fourth, and 

 the fourth from the fifth segment. The terminal segment 

 is short, subquadrate. The first antennee are wanting. 

 The spine-row of the mandibles has but two components 

 on the left mandible, and is reduced to one on the right. 

 The two pairs of maxillae and the maxillipeds have the 



