ZOOLOGICAL AND BOTANICAL ASSOCIATION. 199 



ischium of the posterior pleopods, as regards form, separate it from all 

 known genera, but the agreement in characters of the posterior pleo- 

 pods (this alone excepted), telson, and arrangement of parts of the 

 head, induce me to place it in the Porcellionidae, as an osculant genus 

 to Scyphax of the Philoscid©. Porcellio Wagneri (Brandt) shows an 

 approximation to the form of the posterior pleopods. 



Family.— PORCELLIONID^. 



Genus. — Deto ( Guerin Meneville). 



Body convex. Head : lateral lobes well developed. Internal an- 

 tenna? three-jointed. External antennas : peduncle five-jointed ; second 

 articulation rounded, unlobed ; tige four-jointed. Posterior pleopods : 

 peduncle triangular, lamellar ; accessory lobe well marked, arising from 

 base of peduncle. Ischium compressed, trigonal, acuminate. Accessory 

 appendage trigonal, slender. Species, Deto echinata ( Guerin Meneville) 

 Deto White* (n. *.). 



1. Deto echinata (Guerin) ("Mag. Zoolog." CI. vn., Plate xxiv., 

 Figs. 1-4). — Head and cephalothorax granular, and clothed with a double 

 longitudinal line of strong spines. Abdomen smooth ; telson triangular- 

 acute at the apex. 



2. Deto Whitei (n. *.). — Cephalothorax spined : abdomen : first somite 

 smooth ; second to fifth spined. Telson smooth, rounded at the apex. 

 The spines on the second and fifth abdominal rings are sometimes re- 

 placed by rounded granules. 



I have named this well-marked new species after Adam White, Esq. 



The examination, through the kindness of that gentleman, of the 

 typical specimen on which M. Guerin Meneville founded this genus, 

 enables me to refer this genus positively to the family Porcellionidae, 

 the number and form of the joints in the tige, and the spiny armature 

 of the body, alone separating it. Porcellio echinatum (Lucas) approaches 

 it very closely in this last character. It also displays considerable affi- 

 nity to the genus Acanthoniscus, ( White), but at present it would be 

 unadvisable to unite the two in the one family. 



Genus. — Pybgonisctts. (A. White in lit.) 



Body flattened. Head transverse; frontal lobes cleft in centre, 

 arising from cephalic ring, broad, squared, passing out on each side, and 



ZOOL. * BOT. SOC. FBOC VOL. I. 2 B 



