DR. JOHNSTON ON THE ACARIDES OF BERWICKSHIRE. 229 ' 



but in his Systema he has confounded it with another spe- 

 cies, and has given it an erroneous specific character, for the 

 palpi are not terminated, in our animal, by two bristles or 

 seta;, but by several of the same kind as those on the sides. 

 The Acarus longicornis of the Systema is therefore a mixed 

 species ; but the name ought to be restricted to the mite now 

 described, being that Linnaeus had immediately in view, as 

 is obvious by his reference to the Fauna Suecica. The Aca- 

 rus longicornis of Muller and Otho Fabricius is a different 

 insect ; and so also is the Bdella rubra of Latreille and La- 

 marck.* 



In the description it is said that the back is divided into 

 " compartments," — not a very definite word as here applied, 

 but I could not find a better, for they are not plates nor 

 scales, but subquadrangular divisions, formed merely by a 

 thickening, as it were, of the skin. 



I cannot refer this Acarus to any of the families defined 

 by Dug^s, nor to any of his genera. 



4. Acarus littoralis, Lin. 



Acarus petrarum obscure rufus, pedibus sanguineis, Linn. 

 Faun. Suec. p. 349, no. 1206. — Acarus littoralis, Lin. Syst. 

 1026. Mull Zool. Dan. prod. 187, no. 2222. Fahnc. Faun. 

 Groenl. 225. Turt GmeL iii. 706. Stew. Elem. ii. 323. 



Hab. On the sea-shore, on rocks above high-water mark. 



Desc. Acarus of an ovate form, very dark red with scarlet 

 legs : Bod^i ovate, uneven, rounded posteriorly, narrower and 

 rostrated in front, of a very dark red or almost black colour, 

 clothed with a white appressed hirsuties ; front separated by 

 an uneven elevated line, lighter coloured than the body: 

 Rostrum one-third the length of the body, red, porrect, thick- 

 with a suddenly narrowed lanceolate sharp point, apparently 

 two-valved : Palpi inserted on the base of the rostrum and 

 e<jual to it in length, rather thick and curved towards the 

 slightlv incrassated apex which is terminated with two mi- 

 nute claws ; of a scarlet colour, hirsute : Legs 8, 6-jointed, 

 alike in form, filiform, hirsute, longer than the body, tlie two 

 anterior pairs distant at their origins from the posterior 



• Of this insect (« Bdella longicornis) see a figure in Griffith's Cavior, xiii. 

 p. 506, pi. 22, fig. 8. 



R 



