238 Dr. A. S. Packard, Jnn., 07i Insects 



Marine Insects from Deej) Water. 



During his explorations at Eastport in the past summer, 

 Prof. Verrill dredged, at the depth of 20 fathoms in Eastport 

 liarbour, a Larva of Chironomus oceanicus, Pack. (Proc. Essex 

 Inst. vol. vi. p. 42). It does not differ from specimens found 

 by me at low-water mark in Salem Harbour. It is evidently 

 the same as the supposed larva of Micrahjnima (?) mentioned 

 and rudely figured in the ' American Naturalist,' vol. ii. 

 p. 278, found by me many years ago at low-water mark in 

 Casco Bay. It is of the same size as the Salem specimens, 

 being '25 inch in length. 



Thalassarachna Verrilln, n. sp. — This species differs in 

 important particulars from our best-known species, Hydrachna 

 formosaj Dana & Whelpley (Amer. Journ. Sci. 1836, xxx. 

 p. 354) , found near New Haven, in freshwater Unionidte. The 

 body of that species is much longer, the maxillary palpi are 

 stouter, and the relative length of the joints very different j 

 the claws are very different, the forks of each claw being 

 large and of equal size, and there is no brush on the base of 

 the claw. At first I was disposed to place this halophilous 

 species in the same genus as Dana and Whelpley 's Hydrachna 

 formosa and H. jpyriformis ; but having since then, through 

 the kindness of Prof. Verrill, had the opportunity of studying 

 a freshwater mite closely allied to //. formosa^ which is de- 

 scribed below*, I am led to consider the salt-water mite 

 the type of a new genus, Thalassarachna , with the following 

 differential generic characters : — A conical head distinct from 



• Hydrachna tricolor, n. sp. Under tins name I describe a beautiful 

 mite, brought me from New Haven by I'rof. Verrill, after the present 

 article was sent for publiciition. It is 6-07 inch in length, including the 

 palpi. It is elliptical in form, a little broader behind, being two-thirds 

 as broad as long. Ocelli situated over the insertion of the second pair of 

 legs, the distance between them equal to half the width of the body. 

 Body orange-red, middle portion of the body_ black-brown, due to the 

 colour of the large liver, with a Y-shaped mesial line, pale straw-yellow 

 in colour, formed by the interspace between the two halves of the liver ; 

 the forks of the Y clavate. Appendages very pale grass-green. Legs 

 much as in II. formosa, but the hairs are longer. IMaxillary palpi tlie 

 same as in II. formosa, there being two pairs of minute spines on the 

 fourth palpal joints. Mouth and lancet-formed organ (languette) pro- 

 truded as in II. formosa. " Bitid linguette " at the base of maxillary palpi 

 as in H. formosa. The rudimentary mandibles form a conical protube- 

 rance, the base situated within the body, each mandible being twice as 

 long as broad, and reaching to the basal third of the second maxillary joint. 



Twelve eggs, ten of them fully formed, being as long as the basal joints 

 of the legs, could be seen on the underside of the body. The mite was 

 alive December 30, showing that the eggs, probably laid in the spring, 

 are formed in the preceding autumn. 



