46 G. 0. Sårs. 



In spite of the unusually elongated setæ on the antennæ, 

 the swimming movements of the animal are by no means 

 rapid, and are effected in the usual somewhat tremulous man- 

 ner, the body being kept in a horizontal attitude, with the 

 back downwards. No doubt the antennæ have their chief 

 significance in assisting the powerful tail to pull the animal 

 easily through the loose bottom-material. 



Not more than 2 ova or embryos lying side by side 

 were ever observed simultaneously in the matrix,; but not- 

 withstanding this apparently inconsiderable degree of ferti- 

 lity, the increase of individuals went on rather rapidly. At 

 the close of the season resting ova were produced by the 

 greater number of the specimens, accompanied by a slight 

 change in the upper part of the carapace, which also, in such 

 cases, assumed a somewhat darker hue, though no true ephip- 

 pium was formed. Only a single such resting ovum was 

 found in each individual, and in the exuviation this ovum 

 becomes covered by a part of the moulted carapace. Simul- 

 taneously with this production of resting ova, male specimens 

 were found rather plentifully, being easily recognized by the 

 far less produced rostral projection, and the strong, brownish- 

 coloured hook on the 1st pair of legs. 



Occurrence. — The aquaria in which this form was 

 observed, were all prepared with mud from the neighbour- 

 hood of Sâo Paulo. 



17. Leydigiapsis megalops, n. sp. 



(Pl. VIII, figs. 12—14). 

 Specific Characters. — Female. Carapace, 

 seen laterally, oval quadrangular in form, greatest height 

 somewhat in front of the middle, and not nearly equal to 



