120 Proceeditifis of the Rof/al Irish Acadcinfj. 



referable to some known species^ Shore of oyster pond at Ardfry, 

 in the Orange Lichen and Pelvetia zones, under stones on muddy soil in a 

 spot flooded at higli tides, June, 1916. At Mulranny it was found under 

 stones on the shore, and also in old nests of Puffins and Black-backed Gulls 

 on The Bill Bocks, off the coast of Mayo, June. 



Hydrogamasus littoralis (G. et R. Can.). PI. XXI, fig. 3.) 



1851 ? Gamtunts snlinits Laboulbenc 30, p. 297. 1851 ? Gamasvs 

 marUimus Laboulbene 30, p. 298. 1885 Gamasu* littoralis G. et E. Can. 

 23. p. 72. 1889 Gamas\is littoralU Moniez 38. p. 186. 1892 Hydrogamasus 

 littoralis Berlese 2. Fasc. LXvni, n. 6. 1902 llydrofiamasus salinus 

 Oudemans 41, p. 286. 



In the above-quoteil references it will be seen that Oudemans has revived 

 •' salinus " as the correct sjiecific name for the present species, arguing that the 

 raite figured by Laboulbene as " Gamasu* talinus" is the nymphal stage of 

 //. littfimlii (G. et R Can.), ind he also refer? to the similarity l>etween the 

 original figure of " Gamasus Mlinus" and Iterlese's figure (2) of the nymph of 

 the present species. Doubtless Laboulbene was dealing with a nymphal form 

 of Hydrogamasus. but there are at least three littoral species in this genus, and 

 there is some uncertainly concerning the exact species dealt with by the 

 French author. In a case of this kind it seems best to adhere to the first 

 undoiibtc<l description of the species, which is that of the Italian authors, 

 G. and K. Canestrini. 



During our work at Malahide I was fortunate in finding what are 

 apparently the protonyniphal and deutonymphal forms of If. littoraiis ; they 

 <K«un<d on three occasions in the Vesiculosus and Sernilus zones in company 

 with the adult form. In the protonymph (fig. 3) the primitive arrangement 

 of the dermal platt-s is well shown. It will be remembered that the adult 

 llydrogamasus has the entire dorsum protected by a strongly chitinized 

 shield. In the prot<<nymph there are two large dorsal shields, and between 

 these there are no less than four pairs of very small plates ; there are also 

 three pairs of small plates on each side of the first shield. The second dorsal 

 shield is placed at the extremity of the body, and it is continuous with the 

 .small anal plate on the ventral surface. The sternum is of the usual V-shape. 

 The length is 640^, breadth 370^. 



ITie dcutonymph (length 768/i, breadth 460^) occurred with the adults 

 in October. In this form there are the usual two dorsal shields ; the first of 

 these is the larjer, r it of the ppitonymph, except that the sides, 



frtjm the humeral t-. ... ,....: comers, are {larallel ; the former are well 



