's RIJKS MUSEUM VAN NATUURLIJKE HISTORIE — LEIDEN. 87 



O. gammarellus may be distinguished by the propodite of the first gnathopod 

 being somewhat narrowed at the base and expanding towards the apex 

 in 0. bottae, nearly exactly quadrangular in 0. gammarellus (compare 

 f. 2 and f. 3). It is this feature that Chevreux (p. 159 f. 4) has pointed 

 out in distinguishing the females of the first named species from those 

 of other species of this genus. 



0. bottae has been first recorded from our country by Hoek (Tijdschr. 

 Ned. Dierk. Ver., ser. 1 Deel IY, 1879, p. 130—134), who examined 

 specimens collected at Zalt-Bommel, afterwards it was found by Everts 

 (Tijdschr. Ned. Dierk. Yer., ser. 2 Deel I, 1887, p. cxlvii) in a cellar 

 at the Hague. In recent years the species has proved to be not uncom- 

 mon in the neighbourhood of Leiden. Mr. van Heurn collected it in the 

 Hortus Botanicus in 1911, and in the two or three last years it was 

 observed repeatedly at different localities around Leiden by Mr. P. P. de 

 Koning, one of the preparators of the Museum. It keeps to moist places, 

 hiding under moss, dead leaves and stones, together with wood-lice and 

 beetles, and occasionally jumping about with great agility. These habits 

 have been mentioned by several writers (i. a. Nebeski, p. 32 — 33 and 

 Hoek 1. c). My largest specimen measures 22 mm. The original dark 

 colour very soon disappears in alcohol, but a faint reddish hue may 

 remain some weeks after preservation at the antennae and the last joints 

 of the pereiopods. 



Outside the mediterranean region and that of the Black Sea, the species 

 seems to be very locally distributed. I do not know of any record from 

 Great Britain, Danmark or Norway. From Alsace it has recently been 

 recorded by Lienhart (C. R Soc. Biol. Paris, t. 75, 1913, p. 603). 



For the use of those who take interest in the discrimination of the 

 Talitridae to be found on our shores or inland, I have tried to give a 

 key, partly based on the diagnoses of Stebbing in his „Amphipoda" 

 (Tierreich, Lief. 21, 1916). 



1 Both sexes: first gnathopod simple; second gnathopod with 



broad, membranous carpo- and propodite and excessively small 

 dactylus, as is usual in females of Talitridae. Inferior antennae 

 sometimes half as long as body or still longer. Very common 

 species on the sea-shore 



Talitrus saltator x ) (Montagu) 

 (= T. locusta (Pallas)). 



1) The female of Talorchestia brito Stebbing seems, according to Stebbing's description, only 

 to be distinguished from Talitrus by a somewhat different shape of the propodite of the second 

 gnathopod (see above p. 280). 



