REV. A. MERLE NORMAN, M.A., ON THE CRUSTACEA. 271 
Total length nine tenths of an inch. 
The type specimen was dredged in deep water, forty miles off 
Tynemouth. Within the last few weeks I have had the oppor- 
tunity of examining another specimen which was taken by Mr. 
Jeffreys in the Shetland Seas. This specimen which in all 
respects agreed with that dredged on this coast was sent to me 
for examination by Mr. Spence Bate, in whose collection it is pre- 
served, and who had attached to it a MS. name, unaware 
that I had characterized this species at the meeting of the British 
Association this autumn. 
Mysis didelphys is a much stouter species than M. vulgaris, to 
which it is nearly allied. The antennal scale is less produced, 
and the second jomt much shorter and terminates in three cilia 
instead of in an acutely pointed spine. The telson is also 
shorter, with fewer lateral spines, and has not the two inter- 
mediate apical spines, which are present in MV. vulgaris. Mysis 
didelphys is found in the open sea at a considerable distance from 
the coast, while the habitat of J/. vulgaris appears to be in- 
variably the brackish waters of estuaries and salt marshes. 
Famity. Diastylide. 
This curious and abnormal family was well represented by 
Diastylis Rathku (Kroyer), Hudora truncatula (Spence Bate), 
Vaunthompsonia cristata (Spence Bate), and the three following 
species, which do not appear to have been hitherto described. 
Genus. VAUNTHOMPSONIA, Spence Bate. 
VAUNTHOMPSONIA ROSEA, n. sp. Pl. XIIL, figs. 1-3. 
Vaunthompsonia elongata, flayescens maculis roseis minutis 
numerosissimis picta; segmenta quinque thoracis poster- 
iora a cephalothorace nudata ; pedes abdominales nulli ; 
telson elongatum, appendicum caudalium exteriorum pe- 
dunculo par longitudine, spinis septem terminalibus, 
duobusque utrinque gracilibus armatum ; appendicum 
caudalium pedunculus interne spinosulus; ramus interior 
triarticulatus interne spinosulus ; ramus exterior biartic- 
ulatus paucis ciliis simplicibus instructus. 
