180 PROCEEDINGS OF THE NATIONAL MUSEUM VOL. 97 
Gordon (1932), Chaetonymphon Sars, 1891, is reunited with Nymphon 
J. C. Fabricius, 1794. The three species occurring in the western 
North Atlantic, which have been previously referred to Chaetonymphon, 
form a natural group and are considered under group A of the genus 
as a matter of convenience (fig. 9). 
The former inclusion of Paranymphon Caullery in the Nymphoni- 
dae is not so much an indication of its natural relationships as it is of 
the artificial nature of the families in the Pycnogonida. It differs 
from all the Nymphons in having an unsegmented body and blunt 
7-jointed palpi. In its assemblage of anomalies it resembles Ainigma 
Helfer (1938). 
Ainigma ornatum is a small, delicate form from the Agulhas Bank 
off South Africa, having very high dorsal tubercles at the ends of the 
lateral processes, tapered tarsal joints without auxiliary claws, and an 
oviger with a few large denticulate spines and a simple large terminal 
spine. These characters it shares with Paranymphon spinosum, but 
the segmented trunk, large proboscis, 2-jointed chelifores (the chelae 
are mere knobs), and 9-jointed palpi of Ainigma entitle it to a place 
in the Ammotheidae. The genital protuberances are on the femurs 
instead of the second coxae. One is inclined to wonder whether these 
two queer genera are not more closely related to each other than they 
are to the families in which they have been included. Therefore I 
have removed Paranymphon from the Nymphonidae and placed it in 
the Ammotheidae. 
Four genera are included in the Nymphonidae, one of which 
(Boreonymphon) is monospecific. Pentanymphon and Heteronymphon 
are represented by two species each. Following is a key to the genera 
of the Nymphonidae: 
Peng ptEGe? FERRO eine eee eo re earn rea ee 2 
Five pairs of legs (Antarctic) --__ = 222-222-2221: Pentanymphon Hodgson 
2. Fingers of chelae denticulate, eye tubercle usually present____--.--------- 3. 
Fingers of chelae not denticulate, strongly bowed and with opposed tips; eye i 
tubercle reduced to a minute pimple (Arctic)... Boreonymphon G. O. Sars 
3. Eye tubercle at base of neck between first pair of lateral processes; oviger with 
Tenn laweeeet See ee ee eee ee Nymphon (p. 180) 
Eye tubercle forward, near base of chelifores; oviger without terminal claw 
(Amtierciio an? sar te oi bal perc ope ola blocs Heteronymphon Gordon 
Genus NYMPHON J. C. Fabricius, 1794 
(including Chaetonymphon G. O. Sars, 1891) 
Chelifores 2-jointed, chelate, chelae well developed. Palpi 5- 
jointed. Ovigers present in both sexes, 10-jointed, terminal joints 
with denticulate spines and a terminal claw on the last joint. Body 
segmented, usually elongate but never tightly compact. Propodus 
without heel but usually with auxiliary claws. 
