KNOWLEDGE OF THE HYDRACHXIDAE. 283 



^straightened ventral border ; general colour of body deep Indian 

 red, with a pale ochreous band produced down the centre of the 

 dorsal region, legs and palpi ochreous yellow with black spines ; 

 genital plates elliptical, very prominent, not conspicuously 

 hirsute, surface of cuticle finely areolate. 



This species is jDrominently distinguished from all the forms 

 hitherto referred to the genus JIarica, either in its broader 

 .sense as first established by Koch or, as here delimited, by the red 

 hue of the general area of the body, green, yellow, or brow^n 

 alone being the equivalent tints of the forms previously described. 

 The contour of this species as seen in profile view is much more 

 orbicular than that of either J/, niuscidus or J/, ovalis, and as 

 compared with the former of the two above-named species of 

 which we alone have, through Neuman, any minute structural 

 <letails it (htFers in the much less conspicuous development of 

 the marginal fringe of hairs upon the genital plates and cor- 

 respondingly smaller relative size of those accompanying the 

 gland -apertures developed at intervals along the median dorsal 

 line. Neither has the writer been able to detect in the present 

 species any finely serrated spines at the joints of certain of 

 the legs, as observed by him, but not hitherto recorded, of 

 Marica micscuhcs. So far but a single example of this species, 

 taken from a pond on Wandsworth Common in April 1869, has 

 been collected by the writer, and it has not been thought 

 advisable to take this type-specimen to pieces to examine the 

 possibly slightly varying characters of the mandibles and palpi 

 <as compared with those of the form last named. The members 

 of the genus 2Iarica in accordance with the writer's experience 

 must be reckoned among the most sparsely represented generic 

 groups so far as this country is concerned, since during many 

 seasons devoted to the colleciion of these Water-mites but 

 <x single example of Marica musculus only has been obtained 

 in addition to the solitary specimen of the new form here 

 introduced. 



With reference to this specimen of 2L. musculus several struc- 

 tural points were observed by the writer that appear to have 

 escaped the attention of Neuman when making his drawings and 

 diagnosis of the species. More especially no reference is made to 

 the delicate areolation of the indurated cuticular surface, which 

 in this respect coincides closely, except for its finer character, 



