1926] Schmitt, Crustaceans Collected by the Congo Expedition 15 
Of all the characters, the rostrum of C. togoensis seems to be the 
most variable, and it is upon this character that the distinction of the 
three described varieties of this species from the typical form has been 
based. The first of these, C. t. var. stuhlmanni, with its apparently re- 
duced number of teeth on the upper margin of the rostrum is possibly 
the most extreme variant. The length of the rostrum and its distal 
tooth-free portion is not unusual, nor the teeth on the ventral margin. 
Though in C. togoensis, as here defined, out of the 133 Stanleyville speci- 
mens examined, but 7 have 14 dorsal teeth on the rostrum, and 10 speci- 
mens 15 teeth, his admission of a range including 18 dorsal teeth includes 
the number of teeth occurring with greatest frequency in our material; 
20 specimens had 17 teeth above, 23 eighteen teeth and 21 nineteen teeth. 
The width of the carpus of the first pair of feet as stated is a little broader 
than in the specimens I have examined. Bouvier’s figured C. t. var. 
decorsei with a carpus 2.3 times as long as broad is nearest the 2.5 times 
long as broad carpus of C. t. var. stuhlmanni. Otherwise the description 
fits that of typical togoensis rather closely. 
Given a fair series of C. togoensis, it is impossible satisfactorily to 
distinguish C. ¢. var. decorsei as a distinct variety. A lot of 81 specimens 
could be separated into two series, the one approaching the decorsez 
type and the other approachirig what might be considered typical 
togoensis, with teeth running to or near the tip, and having shorter 
rostra. Nevertheless, the number of intermediate forms, though 
arbitrarily placed with the group to which they seem to belong, was 
sufficient to form a continuous intergrading series. A few such inter- 
eradations have been graphically presented as text figures 1 to 1d. 
It would appear that toothlessness near the tip is largely a function of 
rostrum length, though not absolutely so. This relationship is also ex- 
hibited in the accompanying tabulation, where the more typical togoensis 
forms have the shorter rostra, as compared with the decorsez type. In- 
spection shows, however, how much the two series overlap. In the origi- 
nal description of togoensis the usual number of rostral teeth is given as 
about *'; the count occurring with the greatest frequency in the present 
material is 42. As regards the figure 242°, considered by Bouvier as 
the eonaGete occurring one in decorset, there is not so close an agreement 
though extremes of his range of variation, 242+ and *42+ admit 39, not 
quite a third, of the 133 Stanleyville specimens examined. 
The rostral formula of C. ¢. var. breviatus coincides almost exactly 
with the range of the number of teeth based on 133 specimens from 
Stanleyville, with the exception of one specimen having but twelve 
