Description oj Genera and Species. 21 



sufficiently transparent to allow of the sternal organs and limbs to be seen through it, 

 so that one can make out the palps of the mandibles, the wide sternal arches, the 

 endopodites and exopodites of the limbs, as well as the breeding lamellaj, from which it 

 is evident that it represents a full-grown female. Figs. 3, 3*, are also from GuUane, 

 and represent another adult female. Fig. 2 is from a specimen M. 4249" from 

 Tweeden Burn, near New Castleton, Eoxburghshire. It is one of those figured by R. 

 Etheridge, jun., for hi.s description of the species.' It shows the longitudinal keels on 

 the carapace and the continuation of some of these as ridges on the tail better than 

 the Gullane specimens. It also shows the nature of what was doubtfully considered to 

 be the remains of a large chelate liml) of a Decapod. The massive first leg on the right 

 side is seen to be overlaid by the antennal scale and a broken part of a carapace of a 

 small specimen of the same species. There can be no doubt of the Schizopod nature of 

 the specimen, as the broken lashes of some of the exopodites are seen emerging from 

 beneath the edge of the carapace on both sides of the carapace. Fig. 5, M. 4249", is 

 also one of those figured by R. Etheridge,- and occurs on the same slab with figs. 2, 6. 

 This is evidently a male, and shows that they were of slightly more slender form than 

 the females. It shows the antenimles and antenna;, the large eyes with the ocular papilla, 

 the curved rostrum, and longitudinal keels of the carapace interrupted by the cervical 

 fold. The palps of the mandibles and several of the trunk limbs, with both endopodites 

 and exopodites, are also well shown, as well as the details of the tail segments with the 

 longitudinal ridges, also the pleopods with spatulate termination, and the nature and 

 arrangement of the uropods. The telson with its central crest which, seen edgeways, is 

 shown to be slightly crenulated, is also seen to l)e supplied with accessory swimmerets 

 and to be fringed along its edge with an evenly set row of setaj. This is altogether 

 one of the most elegant and best preserved specimens in the collection. Another speci- 

 men from Tweeden Burn figured by E. Etheridge^ is represented in fig. 4 to show the 

 exopodites of the seven trunk limbs on the left side free from the edge of the carapace, 

 their Ijases being traceable inside it, the bases of the corresponding limbs of the 

 right side being shown within the edge of the carapace on the other side of the wide 

 sternites. The exopodites of some of the limbs, as well as several of the breeding 

 lamelhe, are seen on the left side. The chief point of interest, however, is that the 

 sternal branches of several of the gills are well displayed on the right side. The more 

 intimate structure of one of these is shown raaunified 20 diameters in fig. 4\ 



' Quart. Jouni. Gool. Soc, 1879, vol. xxxv., pi. xxiii., tig. 4. 

 - Loc. cit., fig. 6. 

 3 LciC. rit., tig. 9. 



