(dr. a. c. oudemansX new list of dutch acari, II. 17 

 12. Genus Seiulus Berlese. 



Koch created a genus Seius in 1836 (Deu. Crust. Myr. Ä.rachn. 

 ■4, 17) with Seius togatus as type. 



In 1842 the same author choosed his Sems vulnus as type for 

 the same genus. This is not allowed, but Koch was ignorant of 

 our present Rules of Nomenclature. What this Se'ms vidiius is , 

 is not certain. Berlese believes it is his Epierius glaber. Con- 

 sequently Seius Koch, 1842, is quite another genus as &»w Koch, 

 1836. 



In 1881 Berlese (in Att. R. 1st. Ven. Sc. Lett. Art. (5) VIII, 

 p. 37) created a third genus Seius (the genus in question) with 

 Seius eckinatus Koch as type. As the name Seius is preoccupied 

 (see above), the name Seius Beri, must be replaced. 



In 1887 Berlese (Ac. Myr. Scorp. I tal 41, 3) proposed the 

 genus (sic I) Seiulus for the protonymphae of the species of his 

 Sems (Berlese, 1881) Type Seiulus Jiirsutigenus Beri. 



I am of the opinion that there is reason enough to adopt the 

 name Seiulus Beri., 1887, to replace his genus 6ei«^ (Beri., 1881) 

 which, according lo the Rules of Nomenclature cannot be used, 

 as it is preoccupied. 



13. Seiulus plumosus Oudms., nov. sp. 

 (With Plate 1, fig. 15—19 and Plate 2, fig. 20—21). 



Protonympka. Length 262 ^«. — Colour very pale. — Dorsal side 

 (Fig. 15). On the dorsum the six characteristic rows of hairs are 

 present. These hairs have lateral transparent blades, with denti- 

 culated edge, which give to the hairs the aspect of feathers 

 (Fig. 16). 



The legs are short and thick. 



The epistoma is triangular. 



Ventral side (Fig. 17). There is a distinct sterni-geniti-ventral 

 shield. The anal shield is small. On the sides of the anal shield 

 there are two hairs of the usual type. 



Tijdschr. v. Entom. XLV. 2 



