HORN EXPEDITION—CRUSTACEA. 
237 
posterior extremity, dorsal margin almost straight in the middle, ventral gently 
curved, anterior extremity short and broad, blunted at the tip, posterior extremity 
somewhat produced and narrowly rounded at the tip.” Seen from above, 
the anterior is bluntly and the posterior narrowly pointed. “ Valves with 
numerous very distinct and somewhat elevated lines of growth.” On these, setie 
are usually present in spirit-preserved specimens, and in some varieties are 
extremely numerous. The colour of the carapace varies from light yellow to dalk 
brown. Length of adult (male and female) varies from 4 mm. to 9 mm. 
Locality .—Common in water-holes along the Finke and its tributaries, also 
in the Macumba and Stevenson Rivers. 
We have found it convenient to separate the species into three varieties, the 
extreme forms of which are clearly distinct from one another, but the occurrence 
of intermediate forms renders it impossible to place them in separate species. For 
the purpose of distinguishing the varieties we have taken the form of the carapace, its 
size and sculpturing, the number of lines of growth, and to a lesser extent the form 
of the telson. 
E. packardi, var. typica. 
Measurements of an average-sized specimen—Length of carapace 7'2 mm., height 
5 mm., thickness through both valves 3 mm. Some specimens reach the length of 
9 mm. Lines of growth about 24, well marked. Setie usually present on the lines of 
growth, but sometimes absent. Sars says none are present. The interspaces 
between the lines of growth are marked with raised lines which are vernjiculate 
in the umbonal region. Towards the outer margin they gradually become more 
definitely arranged in a radiate manner as well defined straight lines with their 
inner ends branching and anastomosing. 
The carapace is more compressed than in the two succeeding varieties, and its 
colour in spirit is chestnut-brown with a broad, light band round the margin. 
The spines on the dorsal edge of the telson are numerous and fairly equal in 
size and shape. 
E. packardi, var. cancellata. 
Carapace very tumid. 
Measurements of average-sized specimen :—Length, 8 mm.; height, 6 mm.; 
thickness, 4 mm. 
