Annals of the Transvaal Museum. 
11 
the verge of the ventral surface besides those belonging to the series. The 
anal segment is curiously swollen, and separated by a constriction from 
the segment in front. It is a question whether the segment in front of the 
apparent anal segment is the preanal or the fourth central. If the latter, 
the seeming anal must be compounded of two segments. The first foot- 
joint has an annular swelling near its posterior extremity. The foot is 
four-jointed. The spurs are somewhat slender, divergent, acuminate, 
without interspace. Teeth two ; antenna 4 of neck width ; length, 
creeping, 225^. 
Second (Fig. 4). — The series of spines on the trunk are as in the 
first variety, but they are larger and obtuse. The anterior row has fewer 
spines. There are no prominences on the anterior margin of the trunk. 
The spines of the rump differ from those of the preceding variety — 
especially there are two longish curved lateral spines, which have not 
been noted for any other variety of the species. Collar very prominent ; 
discs separated by a narrow, deep sulcus; central pap llae and setae on 
discs ; length of antenna equal to \ to of diameter of neck. Teeth 
two. Only the second series of spines continues right across the ventral 
side. Length, 300^. 
Third (figs. 6a-6c). — Distinguished from the two preceding varieties 
by the reduction in the number of spines. There are no transverse rows, 
and there are only two lateral spicules belonging to the anterior row, and 
two lateral spicules on the anal segment. The longitudinal skinfolds are 
very prettily scalloped. The foot is slender, and without annular swelling. 
The spurs are slender, incurved, and are separated by a small interspace. 
The collar is very prominent, and the narrow sulcus between the discs 
is quite filled by a large “ ligule ”. Teeth two. 
These extreme forms indicate a wide degree of variability, but the 
whole group to which they belong is excessively variable. Till recently 
I did not suppose C. acuieata to be closely related to what has been called 
the multi pirosa group. The second variety described above has the 
slender lateral spines on the rump which are eminently characteristic of 
that group. 
The muitispinosa group is a vast congeries of forms, some half-dozen 
of which have been recognized as species, but including a multitude of 
widely diverse forms, which are so linked together that it is often impossible 
to decide to which of several species they should be assigned. I believe 
the group to constitute a genus distinct from Callidina, although it could 
only be distinguished by superficial characters. Such characters have 
already been used to separate genera of Bdelloids — for example, Pleuretra 
Bryce ( 5 ). 
Callidina muitispinosa Thomp. ( 35 ) ; synonym, Macrotrachela 
muitispinosa Thomp. (Plate I, figs. 8-9, and Plate III, figs. 13 14 16-18). — 
Besides approximately typical longspined forms, there occurred five 
distinct varieties. 
First (fig. 13).— A long-spined variety, differing from the type 
chiefly in that the spines are swollen below, and setiform above. A very 
similar variety is known in India, and is figured ( 24 ). The African form, 
while superficially very similar, differs in many little points, in the aggregate 
