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 A HISTORY OF ESSEX for it belongs to the family Pandalidae. Its proper name is P. montagui, Leach. That which Mr. Lovett speaks of as the true prawn, evidently meaning thereby the prawn most familiar to his own countrymen, is Leander serrafus (Pennant). Its companion species is L. squilla (Linn.), and the third Palezmon above mentioned is now known as Paleemonetes variant (Leach). All these shrimps and prawns are included in a great tribe Caridea, in which the third pair of trunk-legs are simple, that is, they do not end in an opposable thumb and finger forming what is called a chela. This helps to distinguish them, not indeed from all the rest of the Macrura, but from a goodly number, including lobsters and crayfishes and also a large assortment of otherwise prawn-like animals. The tribe is divided into four sections, distinguished by characters of the first and second trunk-legs. Crangon vu/garis and the rest of the first section have the peculiarity that the front limbs are subchelate. They have a finger which is prehensile by closing down upon the extremity of the hand, but that hand is not itself so produced into a thumb as to form a nipper like a pair of tongs. In the next section, which includes Pandalus montagui, the distinguishing feature is in that part of the second pair of limbs which supports the hand. This part, often called the wrist, instead of being as usual a single piece, is here subdivided into several small articu- lations, giving it a snake-like flexibility. The three remaining species all belong to the third section, in which the front limbs may be either simple or chelate, and the second have an undivided wrist. Palamonetes. variant has the advantage of being able to live either in salt water or fresh. Of Crangon vu/garis Dr. Sorby notes that it is ' common at all stations especially in the estuaries,' and of Leander serrafus that it is ' very abundant in the open water off the coast but much rarer in the estuaries. The common size is not over three inches but occasionally as much as four.' Of Palinurus vu/garis, the crawfish or rock lobster, he says : ' I have never obtained any in trawling or dredging, but it is caught in traps off Walton-on-Naze.' He further records the little schizopod, Praunus Jiexuosus (Miiller) as ' fairly common in most of the estuaries.' Potamobius pallipes (Lereboullet) is not specially assigned to Essex by Mr. Lovett, but in a note to Mr. Lovett's paper Mr. Cole says : ' The crayfish used to be common, and probably is so still, in the Lea and Chelmer, and is found in some of the streams of the New River Company in prodigious abundance.' On the other hand, Mr. Fred Field, writing from St. Leonard's Road, Baling, in March of this year, on the subject of these same freshwater crayfishes, says ' the Colne which used to be full of them no longer contains any.' The sessile-eyed Crustacea of Essex have not yet received much attention. Of one among the marine Isopoda however I can speak from personal opportunity. In September, 1895, the British Association met at Ipswich, and at the close of the meeting an excursion was made to the oyster-beds of the Colne. On this occasion not only were thousands of costly and delicious oysters sacrificed to science, but later in the day great quantities of freshly caught Pandalus montagui were consumed in the 208