76 Proceedings of the Royal Irish Academy. 



2. A XEW SPECIES OF Chthosius. 



The Chthonius here distinguished as Ohtlionius Holberti was discovered by 

 Mr. J. K Halbert in 1915 at Malahide, Co. Dublin. Four speciiueus were 

 obtaiued : ia Mav, 1 S : and in August, 2 (J 1 2 . They occurred just south of 

 ilalahide Inlet, on a rocky patch (limestone) of sea-shore, under stones, the 

 level being below that of the band of orange-lichens and immediately above 

 that of Pelvctia canaliculata, that is to say just above ordinary high-water 

 mark; but the stones would certainly be overflowed by high spring-tides; 

 these stones were resting on moist shelly sand and gravel ; and they 

 sheltered, in addition to the Chthonius, Aepus nmrinv.s, Gamasid mites, 

 centipedes, insect-larvae, etc. 



Chthonius is already represented in the Britannic list bj- CJith. Hayi 

 L. Koch, C'lUh. orthodadylus (Leach), Chlh. tenuis L. Koch, and Chfh. tctrache- 

 lattis (Preys.): four well-known species, all larger than C/ith. Halbcrti, which 

 is not closely related to any of them. In this genus, as observed by 

 AVith ;6), good specific characters are found everywhere; but especially the 

 teeth of the palp-fiugers- provide valuable distinctions ; and in this respect 

 Chth. Halherti is entirely unlike the other four. In OhtJi. Boyi, Chth. ortho- 

 dadi/lus, and Chth. tennis the fixed finger has large teeth, well separated from 

 each other, triangular, acute, and inclined backwards ; in Chfh. tetrachelatiis 

 it has similar large teeth, widely separated, triangular, acute, and erect ; but 

 in Chth. Halbcrti we find the teeth small, in a dense close-set row, parallel 

 and truncate. Among other characters, the cephalothorax is provided with 

 at least 22 full-sized bristles instead of 20 as in Chth. Eayi or 18 as in 

 Clitli. orthodactylm, Clith. tenuis, and CJith. tetracJielatus, the posterior margin 

 having at leeist 6 such bristles instead of 4 as in'Chfh. Rayi or 2 as in the 

 other three species. For the rest, the arrangement of the bristles is much 

 the same, except that the median lateral bristle has a position more removed 

 from the lateral margin. Other noteworthy features are the prominence 

 of the median point of the cephalothorax and the small less strongly 

 developed eyes. In the median position of the two tactile haii-s of the hand, 

 the presence of bristle-groups on coxae ii. and iii. (and not on coxae i.), and 

 in the general character of the genital opening in the male, this species agrees 

 approximately with the other four. 



Other species of Chthonius with small palp-teeth are known ; but no 

 species has been named from any part of Europe, or indeed from any part of 

 the world, to which the present one can be referred. It is unlikely, how- 



