54 
Both sexes (Fig. 54). Rostrum shorter than in S. latirostris; its lateral 
margins below central part. Antennule shorter than in S. Jatirostris, 
about as long as or a little longer than rostrum. Depression of head 
shield shallow. 
Female. Aesthetes about as long as antennule. Dorso-posterior valve 
prominence rounded or pointed. Denticles of valves very small, 
located only on dorso-posterior prominence. 2-8 pairs of lateral 
prominences on valves. Postabdomen with 7—10 anal teeth on each 
side. Anal teeth gradually decreasing in size proximally. 
Male. Vas deferens opening in middle of anal bay. 
REMARKS. Judging from the available descriptions (Herr, 1917; 
Behning, 1925; Sramek-Husek et al., 1962; Flossner, 1972; Kaminski, 
1975), S. lusaticus has all the diagnostic characters of the subgenus 
Aquipiculus. It differs from all other species of the genus in having 
lateral prominences on the valves. 
NOMINA DUBIA AND SPECIES 
TRANSFERRED TO THE GENUS DAPHNIA 
S. aegyptiacus (Fischer, 1860) has been described from the viciniy 
of Alexandria (Egypt). There is no information about the type 
material. The original description (Fischer, 1860) is rather detailed 
and allows us to attribute this species to Simocephalus s. str. I think 
that contrary to the opinion of Richard (1894) and Sramek-Hukek et 
al. (1962), it is not a synonym of S. vetulus because it has a large 
dorso-posterior valve prominence. Behning (1941) supposes this 
species to be a synonym of S. elizabethae, but I believe that the latter 
differs from all species including S. aegyptiacus in the shape of the 
ventral head margin. Unfortunately, it is impossible to conclude 
whether S. aegyptiacus is a separate species or a synonym of S. 
mixtus or S. vetuloides. 
S. cacicus Moniez, 1889 has been described from Lake Titicaca. 
There is no information about the type material. To judge from the 
original description (Moniez, 1889), this species belongs to 
Simocephalus s. str. But it is difficult to say whether it is in fact a 
separate species. 
S. vetulus spinosulus Stingelin, 1904 has been described from the 
Hawaiian Islands. Stingelin (1904) points out that this variety differs 
from the typical form because ‘es zeigt sich die Tendenz zur Bildung 
einer schwachen Shalenprominenz’. No illustration is given. The 
type material has been lost (Frenzel, 1987). Some authors regard S. 
vetulus var. spinosulus as a synonym of S. vetulus (Floéssner, 1972; 
Frenzel, 1987). The original description shows that this variety 
belongs to Simocephalus s. str., but it does not contain any characters 
important for the identification of species within this subgenus. 
Material from the Hawaiian Islands is necessary to decide this 
question. 
S. serrulatus var. nudifrons Delachaux, 1918 has been described 
from the Andes (Peru). The type was probably not indicated. The 
original description (Delachaux, 1918) is without an illustration and 
contains only one character: the absence of denticles at the head in 
all specimens. That means that it is not S. serrulatus because the 
denticles are the main character of this species. But this information 
is not enough to permit identification. 
S. postidelivis Lai & Li, 1987 was described on the base of fossil 
ephippia from the Tertiary of China (Lai & Li, 1987). Referring to 
the photographs, these ephippia do not differ from ephippia of recent 
species. It is impossible to identify either the species or even the 
subgenus. 
Two species assigned to the genus Simocephalus belong, in fact, 
to the genus Daphnia, as is evident from their original descriptions 
M.J. ORLOVA-BIENKOWSKAJA 
(Studer, 1878; Brady, 1918). This is S. gelidus Brady, 1918 = 
Daphnia gelida comb. nov. and S. intermedius Studer, 1878 = D. 
intermedia comb. non. 
KEY TO THE SUBGENERA AND SPECIES OF 
SIMOCEPHALUS 
Figs 55—59 (picture numbers correspond with couplets in the key) 
1. Fig. 55. 9&0": Postabdominal claw without spines. Inner and outer side 
of claw with fine setules (A). Frons rounded, without denticle (B) 
—  Fig.55. 9 &o": Postabdominal claw with basal pecten of spines at outer 
side. Inner side and distal part of outer side with fine setules (C). Frons 
rounded (D) or pointed (E), without denticlesS. (Echinocaudus) subgen. 
ICD) corcnncocccecoeccencnceotco- on eden becencc oreo rconcecesnor peseeRenebenerenccnoncneserencencecscen 10 
— Fig. 55. 9&0": Postabdominal claw with spines on inner side and in 
proximal part of outer side. Basal part of outer side with fine setules (F). 
Frons right-angled, with denticles, or very rarely without denticles (G) 
(American species S. mirabilis) S. (Coronocephalus) Orlova-Bien- 
kowskaya; L995 <2... s.cses. se eteebeteslcd leek nck ceeeets ee 16 
2. Fig. 55. 9: Ocellus elongate (H) (exception: North American species S. 
punctatus). Anal bay with small anal teeth (I). Dorso-posterior valve 
angle without prominence (J) or with comparatively small prominence 
(K). o&: Vas deferens opening on top of supra-anal angle (L). 
Simocephalus’s. Sties2tha eS. ee a, ce ee eee 3 
Fig. 55. 9 : Ocellus short (M). Anal bay without anal teeth (N). Dorso- 
posterior valve angle with large prominence (O). Oo: Vas deferens 
opening in middle of anal bay or at base of supra-anal angle (P) 
S. (Aquipiculus) Orlova-Bienkowskaja, 1995 .........:cccccsceseeeeeeeeeeees 8 
3. Fig. 56. 9: Ocellus point-like (B). Dorso-posterior valve angle rounded, 
without prominence (A). Occurs in North America ............:::c:eeee 
suedul ton icsthsstarancectdvscvedteaachuvdevederstusnseessee teerert oases S. punctatus sp.nov. 
— Fig. 56.2: Ocellus elongate (C). Dorso-posterior valve angle of differ- 
GME SMAPS. o.cecboece se eesd ava subda ce cbeu ance Paccgueceaect eves ca oe eee 4 
4. Fig. 56.2: Dorso-posterior valve angle with very small prominence 
(D). The most common European species. Occurs also in North Africa 
SP ae ea te Ue aah sR S. vetulus (O.F. Miiller, 1776) 
— Fig. 56.9: Dorso-posterior valve angle with larger prominence (E) 
— Fig. 56.2: Depression of ventral head margin near rostrum shallow, 
sometimes absent (G). Species occur in Australia, Tasmania and New 
GUMS ae pses te ehe vecarse cane ccas Sevan saves eae ces a ids bapessee ye wakes ee eee 7 
6. Fig. 56.9: Diameter of dorso-posterior valve prominence exceeds its 
length (H). Dorsal valve margin protruding backward (I) ...............+.- 
Fy eRe RE CRE EEE CERT era S. mixtus Sars, 1903 
— Fig. 56. 9: Diameter of dorso-posterior valve prominence less than its 
length (J). Dorsal valve margin not protruding backward (K). Occurs in 
BAS term SIDEMAN rerescs-c cere teens See ee S. vetuloides Sars, 1898 
7. Fig. 56.9: Dorsal valve margin protruding backward strongly (L) 
Jadot chavs ous ccca@tter a uravicsaacakasiaedeaaawMenes rane oe een cutee S. gibbosus Sars, 1896 
— Fig. 56.9: Dorsal valve margin not protruding backward (M)........... 
b AO a Marat hn Rt in oo MRED comuccente S. elizabethae (King, 1853) 
8. Fig.57. 9 & &: lateral prominences on valves present (A). Rare species. 
Occurs in East Europe and China..... ..........::cesceecceeeeeeeee S. lusaticus 
Herr, 1917 
