CRUSTACEOLOGY. 



413 



Arachni 

 tie?. 



!*.. Pycno. 



OONUM. 



Balxna- 

 rum. 





I'j.ate 



((XXI. 



i Viz- 11. 



E!cuterosr 

 ma. 



the Scottish coast, in a living state, were of a blood-red 

 colour, and are possibly distinct. 



Family III. Pycnogonides. 



Genus III. Pycnogonum. Brunnich. Muller. 

 Olh. Fabr. Joan Fabr. Oliv. Lam. Lair. Phalan- 

 gium. Pennant ; Gmeiin. mandibules none. 



Sp. 1. Bahenarum. Body rufous or dusky. 



Pycnogonum balcenarum. Fabr. Latr. 



Phalangium balcenarum. Pennant, Gmeiin. 



Inhabits the rocky shores of the European Ocean, 

 getting under stones, or running on the rocks at low 

 water'. It is sometimes also taken by the dredge, in 

 deep water, on many parts of our coasts, but is not com- 

 mon. Mr Sowerby has observed them amongst the 

 oysters in the London shops occasionally. See Plate 

 CCXXI. Fig. 11. 



ORDER II. ELEUTEROSOMA. 



Family IV. Astomides. 



4. Caris. 



Vespertili- 

 ouis. 



5. Leptus. 



A. Palpi and Rostrum very conspicuous. 

 Genus IV. Caris. Latreille. Acarus. Geoff. 

 Rostrum conic and porrected from the maxillae. 

 Palpi somewhat conic, four-jointed, porrected, and 



as long as the rostrum. 



Body coriaceous, somewhat orbicular and depressed. 



Sp. 1. Vesperlilionis. Body brown. 



Caris Vesper tilionis. Latreille. 



Inhabits bats. 



Genus V. Leptus. Latr. Pediculus. Scopoli. 

 Acarus. Shaw, Fabricius. Trombidium. Hermann. 



Mouth furnished with a porrected rostrum. 



Palpi short and someAvhat conic. 



Body soft and generally oval. 

 Phalange. Sp.l. Phalangii. Body oval, bright red, with an 

 elevation in front, and -two black eyes; rostrum some- 

 what conic ; base of the palpi much thickened ; feet 

 nearly equal in length. 



Pediculus coccineus. Scopoli. 



Acarus Phalangii. Fabricius. 



Leptus Phalangii. Latreille. 



Inhabits several insects, especially Phalangium Opi- 

 lio. 



Obs. To this genus, according to Latreille, all the 

 trombidia hexapoda (six-legged trombidia) of Hermann, 

 and the acarus autumnalis of Shaw's Naturalist's Mis- 

 cellany, are referable. 



B. No rostrum ; the parts ofthemotdh very obscure. 

 Genus VI. Astoma. Latreille. 

 Mouth nearly obsolete. 

 Body soft and oval. 

 Feet very short. 

 Sp. 1. Parasiiicum. Body bright red, somewhat 



contracted in the middle. 



Astoma parasiticum. Latreille. 

 Inhabits mosses and insects. 



II. Eight Feel. 

 Family V. Hydrachnides. 

 A. No mandibular. 



Genus VII. Limnochares, Latreille. Acarus^ 

 Linn. Geoff. Do Gecr. Trombidium. Fabr. 

 Palpi bent inward, without appendices. 

 Rostrum scarcely prominent. 

 Body depressed, and tomentose. 

 Feet short, the four posterior ones distant. 



. A.-TO- 



'arasiti- 

 jm. 



ElMNO- 

 URES. 



Arachni 



di-s. 



Ho'ose- 

 risea. 



8. Hy, 



DftAChNA. 



HVDRACHNA. 9. Elyais. 



Sp. 1. Holoserisea. Body ovate, rough and soft, with 

 two black eyes. 



Acarus aquaticus. Linne. 

 Trombidium aquaticum. Fabricius. 

 Limnochares holosericea. Latreille. 

 Inhabits the waters of Europe ; is very common in 

 our ponds during the 6ummer months. It varies in 

 colour, but is most frequently found bright red and 

 greyish red, with all the intermediate varieties of shade. 

 Fabricius says it deposits eggs of a red colour, or nepa?, 

 (water scorpions.) 



Genus VIII. Hydrachna. Mull. Oliv. Lair. Aca- 

 rus. Linn. Geoff". De Geer. Trombidium. Fabr. 



Palpi somewhat cylindrical, porrected, consisting of 

 four joints, the last sharp, and armed with a moveable 

 appendage. 



Mouth produced into a porrect, conic rostrum. 

 Maxilla; two, lengthened, setaceous, and sharp, capa- 

 ble of being concealed by the lip. 

 Body globular. 



Feet placed at an equal distance from one another, 

 fimbriated with hair. 



Sp. 1. Geographica. Body black, with points and Geograpl 

 spots of red. Ca - 



Hydrachna geographica. Midi. Latr. 

 Trombidium geographicum. Fabr. 

 Inhabits slowly flowing waters and ponds. The 

 largest species hitherto discovered. 



Sp. 2. Cruenta. Body blood red ; feet equal. Cruenta. 



Hydrachna cruenta of Muller and Latreille. 

 Trombidium globator. Fabricius. 

 Inhabits the European waters. 

 B. With Mandibular. 

 Genus IX. Elyais. Latr. Lam 

 Mull. Oliv. Trombidium. Fabr. 



Mandibules depressed, armed with a nail at their 

 points, and received within the lip. 



Palpi oblong-conic, bent, sharp, and consisting of 

 three or four joints. 

 Eyes four. 



Sp. 1. Extcudens. Body round, shining, smooth, Extendms 

 and red without spots ; posterior feet very smooth. 

 Hydrachna extendens. Mull. 

 Trombidium extendens. Fabricius. 

 Elyais Extendens. Lamarck, Latreille. 

 Inhabits stagnant waters throughout Europe. 

 Obs. Latreille, in his Genera Crustaceorum el Insec- 

 torum, says, he suspects the following Hydrachna of 

 Muller, viz. undulata, fuscata, maculata, umbrata, to 

 belong to the genus Elyais. This future observers 

 must decide. 



Family VI. Eicinides. 



I. Eyes distinct. Body very soft and thickish, the 

 dorsal skin not coreaceous. 



A. Palpi obscure. 



Genus X. Sarcoptes. Latr. Acarus of authors. 



Sp. 1. Passerinus. Third feet very thick. 



Acarus passerinus. Linn. Fabr. Herm. 



Pulex Sturni. Redi (Opuscul, torn. 1. tab. 2. Jig. 4.) 



Sarcop.es passerinus. Latr. 



Inhabits birds. 



Sp. 2. Scabiei. Body somewhat round; feet short, Scabki 

 reddish ; the four posterior ones bearing a very long 

 seta ; the anterior four terminated by a club. 



Acarus scabiei. Fabricius. 



Sarcoptes scabiei. Latreille. 



Inhabits ulcers in the itch. A good figure is given 

 by Latreille, in his work entitled Hist, natural des Cru$- 



10. Sar- 

 coptes. 

 Passerinus. 



