406 



CRU5TACEOLOGY. 



Crustacea, must content ourselves by extracting tlie description 

 ^T"*"" given by that celebrated zoologist. 



" Oniscus thoracicus. Body oval, inequilateral, with 

 about fifteen indistinct joints, indented at the sides, the 

 six posterior shooting into long, lateral, fasciculate, 

 fleshy, ramose appendages, and the extremity furnished 

 with six simple recurved ones, two of which are larger 

 than the rest. Antennae four, short; the outer pair 

 longest, and only visible above. The two first joints of 

 the body furnished with a long, flat, oar-like, fleshy fin, 

 or cirrus, on each side ; the other joints with similar 

 short ones. Legs fourteen, very short, crooked, and 

 concealed beneath. The abdominal valves are large, 

 cover the whole under part of the body, and form a re- 

 ceptacle for the ova, which are, in specimens before me, 

 vastly distended with many thousands of a pale orange 

 colour. 



" Length, including the posterior appendages, scarce- 

 ly half an inch. 



" Colour usually orange ; lateral appendices whitish. 



" The male is very inferior in size, of a more slender 

 form, and is destitute of the cirri on the anterior part 

 of the body, and those on the posterior joints are sim- 

 ple, not branched, as in the female ; in other respects 

 they agree." 



Mr Montagu says likewise that he has extracted it 

 from under the thoracic plate, and kept it alive in a 

 glass of sea- water for several days. In the few which 

 lie has met with, the male was always found attaching 

 itself to the ventral appendices of the female by its 

 claws. That it forms a distinct genus from any here 

 defined, and is referable to another division of the tribe, 

 need scarcely be mentioned to the scientific reader. 



Family XIX. Oniscides. 



71. Lioia. Genus LXXI. Ligia. The outermost segment of 

 the external antenna? composed of a number of small 

 articulations. A bifid style, placed on a peduncle on 

 each side of the tail. 



Observation. It has been supposed by Latreille, and 

 other authors of eminence, that the number of joints in 

 the last section of the external antennae afforded speci- 

 fic distinctions in this genus; the observations, how- 

 ever, which we have made on L. oceanica and scopu- 

 lorum, fully prove the evanescence of this character, as 

 the joints not only vary in number in the same species, 

 but even in the same individual. 



Sp. 1. Oceanica. Body brownish ; back very rough; 

 sides often beautifully speckled with minute black spots. 

 See Plate CCXXI. Fig. 8. 



Oniscus oceanicus, Linne. Ligia oceanica of Fabri- 

 cius and Latreille. 



Length half an inch. 



Inhabits the shores of the European ocean. 



This, and probably all the species, are very prolific : 



Mr Williams, an ardent student of zoology, found above 



seventy young ones in the abdominal pouch of a female, 



in the month of August. 



Scopulo- &V- 2. Scopulorum. Body cinereous, sides speckled 



riim. with minute black spots ; back somewhat rough. 



Ligia oceanica, variety, Leach's MSS. 



This species, which is probably a variety of the pre- 

 ceding, is very common on the rocky coasts of Devon- 

 shire. It is nearly three times the size of L. oceanica, 

 from which it is readily distinguished by the compara- 

 tive smoothness of its back, and superior size. 



Observation. The above species are all that we have 

 met with. Three others are enumerated by Latreille ; 

 these we shall mention in his words. 



Oceanica* 



i'LlTE 



CCXXI. 



Fl|J. g. 



Crustacea. 

 Iulica. 



Hypno- 

 ru.ii. 



" 3. Itulica. Antennae almost as long ass the body ; 

 the last joint composed of seventeen minute articula- 

 tions ; styles of the tail equal, exserted ; the footstalks 

 narrow and elongated." 



Ligia Italica of Fabricius. 



4. " Hypnorum. Antennae half the length of the 

 body ; the last joint composed of ten minute articula- 

 tions ; the caudal styles exserted, with the point of the 

 peduncle internally produced into a setigerous tooth ; 

 the body above variegated with cinereous and yellow." 



Oniscus hypnorum of Cuvier and Fabricius. 



Oniscus agilis of Panzer. 



Latreille observes, " It inhabits the shores of the Bri- 

 tish Ocean : I received it from the celebrated Brebisson." 



" 5. Oniscoides. Styles of the tail very short, not Oniscoides 

 exserted : the laciniss ovate-lanceolate." 



Oniscus assimilis of Linne. Cymolhoa assimilis of 

 Fabricius. 



" Inhabits the Mediterranean Sea." 



Genus LXXII. Philoscia. External antennae eight- 

 jointed, the base naked. The first segments of the tail 

 abruptly narrower than the preceding joints of the body. 



Sp. 1. Muscorum. . Body variegated with cinereous 

 and white. 



Oniscus muscorum of Scopoli and Cuvier. Oniscus 

 syhestris of Fabricius. Philoscia muscorum of Latreille. 



Is found under mosses and stones in England, France, 

 and Germany. 



Genus LXXIII. Oniscus. The external antennae 

 with eight joints, inserted under the margin of the an- 

 terior part of the head. 



Sp. 1. Asellus. Body above obscurely cinereous and 

 rough, with white longitudinal lines of spots ; the side* 

 yellowish. 



Oniscus asellus of Linne and Latreille. Oniscus mu~ 

 rarius of Fabricius and Cuvier. 



Inhabits rotten wood, old walls, &c. tliroughout Eu- 

 rope. 



It was formerly used in medicine, being supposed 

 to cure agues, consumptions, &c. but is now wisely re- 

 jected from the modern pharmacopoeias. Its vulgar 

 names are common millepied or sotvs. 



Genus LXXI V. Porcellio. External antennae se- 

 ven jointed, inserted under the margin of the anterior 

 part of the head. The lateral styles of the tail conic 

 and prominent. 



Sp. I. Scaber. Body above rough and granulated. 



Oniscus asellus of Cuvier, Fabricius, and Panzer; 

 Porcrllio scaber of Latreille. 



Inhabits Europe. 



This species is found under stones, in rotten wood, 

 and on old walls. It varies much in colour, being at 

 one time bluish black, at another time yellow. In Scot- 

 land it is called sclater. 



Sp. 2. Lcexiis. Body smooth. 



Porcellio Icevis of Latreille. 



Inhabits the same place as the former species. In 

 this country it is rare, one specimen only having been 

 taken by Mr W. E. Leach, in Devon. 



Obs. To this genus, Oniscus convexus of De Geer 

 (Mem. sur les Insect, torn. vii. pi. 35. fig. 11.) appears 

 to belong. 



Genus LXXV. Armadillo. External antennas se- 

 ven jointed, the lateral styles of the tail not prominent, 

 the last joint triangular, and meeting the hinder mar- 

 gin of the posterior margin. Body capable of rolling 

 into a ball. 



Sp. 1. Vulgaris. Body above of a greyish-lead co- 

 lour ; the posterior margins of the segments white. 



72. PHI- 

 LOSCIA. 



Muscorum. 



73. Onij. 



CCS. 



Aiel'ui. 



74. Poucel 



LIO. 



Scaber. 



Lecris. 



75. Arma- 

 dillo. 



Vnlgarit. 



