520 Mr. D. Sharp and Mr. F. Muir on the Comparative 
formed by two pieces articulated together, the distal one bearing 
two small lateral lobes. It is possible that the distal piece is the 
basal part of the lateral lobes, and the basal plate is the basal 
piece. The basal corners of this basal plate meet under the 
median lobe, No differentiated internal sac. 
Chaetosoma scaritides (Pl. LVIII fig. 98). 
Median lobe slender, chitinous on ventral aspect, membranous on 
dorsal ; median orifice on dorsal aspect of tip, ventral edge pointed 
and projecting beyond dorsal edge. Tegmen forming a ring, with 
large dorsal cap-piece formed of a large curved plate with a pair of 
broad lateral lobes at apex; the ring is broad and continued as 
a strut (tg) on ventral side. Internal sac small, not differentiated. 
There are probably more than one species of Chaetosoma 
in New Zealand, and if so the one here dealt with is 
not the C. scaritides of Westw. Ours is a comparatively 
large, black form, found by Commander J. J. Walker at 
Wellington. 
Rhizophagus depressus (P|. LVIII fig. 101). 
Median lobe large, tubular and slightly curved ; median orifice 
at apex, the base prolonged into a long dorsal strut. Tegmen 
forming a slender ring round the median lobe, the dorsal part 
slightly enlarged into a very small cap-piece. Internal sac large, 
with stout, twisted flagellum arising from apex. 
This differs from Nitidulidae by the large, exposed 
median lobe, the cap-piece of the tegmen reduced so as 
not to cover the lobe. 
This family is of great interest and requires much 
greater investigation than we have given it before any 
definite conclusions can be arrived at. It will eventually 
have to be divided. Whether or not certain divisions that 
have already been proposed are adequate we cannot say. 
Chaetosoma is of interest as it shows a probable transition 
from the sheath type (Trogositidae) to the true ring type. 
In Diagrypnodes we have a type nearer to Pythidae than 
to Cucujus. The degree of differentiation of the sac and 
the condition of the lateral lobes must be considered 
in adjusting the relationships in this family, Thus 
Hectarthrwm has a more generalised tegmen than Lthizo- 
phagus wherein its reduction to a mere ring is very 
