DescripUoib of Genera (ind Species. 1 '^ 



approaches most nearly in form and characters to tlie recent Gnatlioplutusia. It is 

 about the smallest species of the genus, averaging about 15-20 mm.; but full grown 

 specimens, as shown by the well-developed breeding lamellje, are found even smaller. In 

 form it greatly resembles T. loudonensis, but is somewhat shorter in proportion, and 

 proportionately wider across the carapace and narrower across the sixth tail segment. 

 The wide carapace generally causes the form to be fossilised so as to be seen back up. 



The carapace behaves to the trunk segments as in Gnathophausia and in the former 

 species, that is, it only loosely covers the last seven trunk segments, and when in place 

 leaves the dorsal part of the last segment quite bare. It is ornamented with all the 

 seven longitudinal keels in addition to the thickened marginal bands. All the keels are 

 interrupted at the well-marked cervical groove. The median keel is continued into the 

 rostrum, which is long and is flanked by side keels and ends in spines as in 

 T. loudonensis. The dorso-lateral keel is also continued in front of the interrupting 

 fold and ends anteriorly in a supra-orbital spine. The dorsal integuments of the trunk 

 segments, with the exception of the last, are quite thin and almost membranaceous. The 

 last segment forms a complete ring, and seems to have been more loosely attached than 

 the others. The sternites of the seven leg-bearing trunk segments are strongly built 

 and the first is narrow and wedge-shaped, the others becoming in turn wider and wider, 

 the whole forming the wide sternum so characteristic of the Schizopoda, and especial!}- 

 of this group. In their form and arrangement these sternal plates are individually 

 almost the counterpart of the corresponding structures in T. loudonensis, and. as in that 

 species, the sternal arrangements are usually to be seen through the carapace.^ 



The tail is shorter in proportion to the trunk than in the type species. The 

 individual segments bear much the same jjroportion to each other as in it ; but the 

 transverse strengthening bands are more pronounced, and there are longitudinal keels 

 on each segment in continuation of the line of the median and dorso-lateral keels of the 

 carapace. In the hinder segments of the tail the panel-like spaces enclo.sed within the 

 areas bounded by the smooth transverse bands and the longitudinal keels are somewhat 

 embossed, the integuments are pitted and wrinkled into a sort of pattern (figs. 1, 2) ; but 

 this is not carried to such an extent as in some other forms belonging to the group. 



The eye is larger in proportion than in the former species, and, as the stalk is short, 

 the taper is necessarily very rapid. The visual [jortion or cornea is large, and was 

 probably pear-shaped. A comparatively large ocular papilla has been observed in 

 several specimens (figs. 4. (i) to proceed from the pedicle on its inner aspect. The 



' Similar bos-ses occur on the sternites of this species and those fouml on T. loudonensis, and doubtless 

 li:id :i similar function, viz.. that of iioldin;,' luminous org.-xns. 



