39 10 Proceedings of the Royal Irish Academy. 



very marked, and the front is produced in a rounded prominence. The colour 

 is a fine scarlet with black-pigmented eyes. The arrangement of the epimera 

 differs from the figures given by Piersig and Protz. In both of these figures 

 the genital area is placed considerably in front of the third and fourth epimera, 

 and shows a row of cone-shaped discs arranged towards the inner margin 

 of the genital field. In the Croaghpatrick example the end of the genital 

 area lies between the third pair of epimera ; and the discs are placed in a 

 groove on the outer side, much as they are drawn in Protzia rotunda 

 Walter (33). 



In his recent useful handbook on German Hydracarina, Koenike figures 

 what he considers to be Protzia eximia; and in this the above-mentioned 

 characters are shown just as they are in the Croaghpatrick specimen (12). 



Protzia occurs commonly in certain of the Dublin and Wicklow streams, 

 though I have not yet ascertained whether all of the specimens collected are 

 referable to one or more species. It is especially fond of small mountain burns, 

 where it lurks in aquatic mosses, or clings to small granite boulders in the 

 bed of the stream. On one occasion, towards the end of September, a number 

 of specimens were collected in a stream on Kilmashogue, Co. Dublin, amongst 

 which were two interesting nymphal forms. 



Nymph. — One of these, measuring - 870 by - 655 mm., resembled the adult 

 in the shape of the body and the arrangement of the epimera. This specimen 

 possessed four rather widely separated, cone-shaped, genital discs (PL I., fig. 8b) 

 similar to those found in the provisional genital area of the nymphs of Thyas. 

 The second specimen is an encysted nymph measuring about - 790 mm. in 

 length, ovate in shape, and covered with much longer papillae than occur in 

 the adult. With the exception of the first and second legs of the right side, 

 the nymphal appendages have disappeared. Inside this nymph-skin all of 

 the folded legs and palps, and, in fact, all the chitinous parts of the adult 

 Protzia, can be clearly seen. The interesting point is that the provisional 

 genital area of this second nymph differs from the four-disked type in having 

 ten rather small genital discs, arranged five on each side, much as in the 

 accompanying figure (PL I., fig. 8«), and these discs are smaller and less 

 cone-shaped. On the outer side of the field there is a row of short, sharply 

 pointed spines. Immediately under this provisional area lies the apparently 

 fully developed genital field of the adult mite. This observation would 

 seem to show that in the genus Protzia there is a well-marked second 

 form of the nymph, following on the four-disked type, somewhat similar in 

 structure to the ten-disked type of Thyas curvifrom Walter, recently 

 described (33) by Dr. C. Walter from Switzerland (Waldquelle bei Parpan, 

 1700 m.). 



