502 Fleterogenetic Development in Diaptomus. [May, 
SCAPHOLEBERIS ANGULATA, sp. nov. (Figs. 26-28, Plate V). 
The genus Scapholeberis at present consists of two species, S. 
nasuta Birge and S. mucronata with its three varieties (a) fronte 
levi, (ò) fronte cornuti of Europe, and (c) armata? found in Min- 
nesota, Illinois and Tennessee. With regard to the European 
varieties it is remarkable that although they are not local varieties? 
the horn upon the head appears in the larger individuals and not 
as would be expected from the analogy of Daphnia, in young 
and small individuals. However, it is to be noticed that the 
spines of the valves in Scapholeberis are not persisting embryonic 
characters like the spine in Daphnia, but the young are like 
Ceriodaphnia. It may be that in like manner the crest upon the - 
head in Scapholeberis is, instead of an embryonic appendage as 
in Daphnia, a later production. It might then be suggested that 
Scapholeberis is now undergoing differentiation or, in other 
words, is a new genus historically, while Daphnia is past the 
acme of its activity in the direction in which it has differentiated 
and now retains its peculiarities by inheritance, and tends to con- 
tinue them only so far as they are of functional value. . 
The horn which sometimes appears in young of certain speci® : 
_ of Daphnia (D. galeata) and seems so capricious in its produc: 
tion, may be not unlike that of this species. ee 
Were it not that S. mucronata is known to be very bees } 
might be admissible to create var. armata a new species. Addi 
tional details are given for this variety in Figs. 23-24, de a 
Scapholeberis angulata, sp. nov.—Head of medium size; rostrum directed oo 
ward and backward; eye of moderate size; macula nigra indistinct ; hago : 
basin for antennz well developed; antennules long curved, armed with abe cal 
sense hairs as well as the terminal olfactory ? filaments; cephalic portion of e 
of antennæ marked by longitudinal lines connected at intervals by Sg” eeg 
rior portion of the part of the basin on the valves reticulate ; “ mucro amiba ; 
in 
‘ 
: 
ferior posterior corner of shell simply sharply angled; inner wall of g ght of the q 
with a row of small spines below and posteriorly for a gen of pore known sp 
shell; caudal teeth 5-7 in adult, being more numerous than in any ° i] 
cies; size large. gä | 
E E E CO i; 
The “mucro” is absent in the smallest individual ohni 
Scapholeberis seems to lie between Daphnia and er nag 
agreeing with the former in heing a divergent ma ABE 
* y ». . LF tal , 4 
ily, but still with more affinities to the latter. Near a] 
1 Birge. Notes on Cladocera. x 
- * Herrick. Notes on Crustacea of Minnesota, Geol. Rep. sine 
3 Kurz. Doclekas neuer Cladoceren, etc., p. 22. 
is aa 
