PACIFIC SCIENCE, VoL XVIII, April 1964 
176 
Gempylus serpens , the jaw protuberance is flex- 
ible (and sometimes decurved in Nesiarchus 
nasutus ) , precluding its use as a spear, and in- 
stead suggesting a hydrodynamic function (cf 
Wisner, 1958: 68). 
Nealotus tripes Johnson 
Station 2 1 specimen: 176 mm 
Station 32 10 specimens: 1 6.4-4 L 5 mm 
Station 49 8 specimens: 19.6-25.8 mm 
Station 51 59 specimens: 10.0-20.2 mm 
Station 53 3 specimens: 10.0-22.0 mm 
Station 56 4 specimens: 9.0-24.0 mm 
Station 58 6 specimens : 21.2-25.0 mm 
Station 60 2 specimens: 21.4-28.0 mm 
Station 70 . 1 specimen: 37.0 mm 
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160° 155° isr 143* 
Fig. 1. Trawling stations on "Hugh M. Smith” cruise 
47, showing places of capture of Acanthocybium, 
Nealotus, and Diplospinus. 
When first examined, the smaller specimens 
listed above were thought to be Nesiarchus 
nasutus Johnson, to which they bear a strong 
superficial resemblance (cf Voss, 1954). Subse- 
quent staining revealed their salient taxonomic 
feature, a reduction in the number of pelvic 
rays, showing that they belonged in a different 
branch of the Gempylidae, the Rexea-Prome- 
thichthys -Nealotus group. According to Grey 
(1953:139), these genera are characterized by 
a reduction of the pelvic fins to a pair of spines, 
or by the total absence of these fins. Only the 
largest of the above specimens, a fish 176 mm 
in length, has the pelvics reduced to mere spines 
and thus is referable to Nealotus tripes. The 
remainder range from 9.0-41.5 mm, and have 
pelvic formulae of 1,2 or occasionally 1,1 (Table 
2). In this length range, as is shown in the 
following paragraphs, the pelvic rays gradually 
become overgrown by abdominal tissues, within 
which they are dearly visible after alizarin stain- 
ing. At larger sizes the rays presumably are too 
deep to be seen without dissection or staining. 
Norman (1930:351) failed to find them in 
N. tripes specimens 53 and 88 mm long. Dis- 
section of the pelvic region of my 176- mm fish 
revealed fragments of raylike material in the 
musculature ventral to the pelvic bones. These 
fragments were fused to the pelvis anteriorly, 
and appeared to serve as anchoring struts. 
In young Nealotus individuals there are two 
prominent spines preceding the anal fin, whereas 
adults are generally regarded as having only one. 
My 176-mm specimen conforms to the adult 
concept externally, but when dissected its peri- 
anal region contained a small, flat spine, tri- 
angular in outline, embedded behind the first. 
Matsubara and Iwai (1952:207) also noted a 
second anal spine, but in their 199-mm fish it Is 
shown as being externally visible. 
With an ontogenetic loss of pelvic rays and 
anal spines, the genus Nealotus (and perhaps 
others) becomes more difficult to define. Charac- 
teristic counts are given in Table 2, along with 
data for Nesiarchus nasutus , a species of similar 
.appearance. 
Figure 3 depicts the smallest Nealotus exam- 
ined, a fish 9.0 mm in standard length. At this 
size the vertical fin rays have not all differen- 
tiated, the dorsal being XX 1, 18 and the anal 
