CEN OME Oh 
Crustacean of the Genus Mysis. 431 
Mysis Spiritus, n.s. Pl. VIII. figs. 1 & 1*. 
Mysis gracilis, pellucidus, vitreus. Thorax cylindricus. Abdomen 
a thorace ad caudam gradatim diminuens; abdominis segmentum 
penultimum longius quam cetera. Appendix antennarum squa- 
miformis subtriangularis, apice acuto; spina in medio marginis 
exterioris posita; margo interior atque exterior supra spinam 
dense ciliati; margo exterior sub spina non ciliatus. Thoracis 
Jrons vix rostrata, fere subtruncata. Pedunculi oculorum longi, 
appendicisque antennarum dimidium superantes. Antenne breves, 
thorace vix longiores. Telson apice fisso intermedias fere sequat 
lamellas ; fissura brevis. 
A perfectly colourless, glassy, transparent species, and, like 
M. Oberon, scarcely to be distinguished except by its black eyes ; 
very slender and graceful in form. Carapace cylindrical, not 
widening behind. Abdomen gradually tapering towards the 
tail. The front margin of the carapace can scarcely be said to 
be rostrate, being very nearly truncate. Antennal scale sub- 
triangular, with the apex acute, not twice as long as the very 
long peduncle of the eye, and slightly exceeding the peduncle of 
the interior antenne; a spine placed half-way up the outer 
margin ; internal and external margins above the spine densely 
ciliated ; external margin below the spine plain. Antenne re- 
markably short, not so long as the carapace; the peduncles of 
the interior exceed their filaments in length. Telson two-thirds 
the length of the intermediate lamellz ; the bifurcation is through 
about a third of its length. 
Taken in sandy rock-pools at the “ Black Hall Rocks,” on the 
coast of Durham. 
The following differential characters may be usefully borne in 
mind by the carcinologist :— 
M. Lamorne has no spine on the antennal scale. 
M. flexuosus has a spine at the apex of a lanceolate, obliquely 
truncate scale. 
M. Spiritus has a spine about the centre of the outer margin 
of a subtriangular pointed scale. 
EXPLANATION OF PLATE VIII. 
Fig. 1. Mysis Spiritus (Norman). [The spine on the antennal scale is 
represented too high up.] 
Fig. 1*. Telson of Mysis Spiritus. 
Fig. 2. Head of Mysis flecuosus (Miiller). 
Fig. 3. Tail of the same. 
Fig. 4. Head of Mysis Lamorne (Couch). 
Fig. 5. Tail of the same. 
Sedgefield, co. Durham, Oct. 22, 1860. 
