Gastrocotyiine Parasites of Indian Clupeoids — Unnithan 
211 
Axinidae), but it is incomplete in all the 
atypical clupeoid parasites described in the 
present study. 
The partition of genera is based on criteria 
which have appeared to be valid for genera of 
other subfamilies of the higher Monogenoidea, 
namely: 
(1) The relative encroachment of the clamp 
rows up the body proper (as distinct from a 
tail-like haptor quite distinct from the body, 
for example in Chauhanea ), which determines 
the zone of pivoting in all the possible feeding 
attitudes of the attached worm. If this pivoting 
zone occurs in the thicker gonad zones, then 
the torque set up will tend to a somatic asym- 
metry (e.g., Rngraulis cobind) ; if, on the other 
hand, it is near or beyond the end of the testes 
zone (as in Engraulicola , Pellonicola, and 
Pseudaxine) , then the highly contractile body 
may be irregular in outline at any one moment, 
but very little permanent strain would be 
registered, and there is no structural asymmetry 
in the body proper. Nor is this asymmetry 
present in forms where the pivoting zone 
occurs anterior to the gonad zone: the fore- 
body alone in these forms is free to bend, and 
again no true somatic asymmetry is developed 
(e.g., Gastrocotyle, Engraulixenus, and En- 
graultphila ) . 
(2) The degree of suppression of one side 
of the haptor. It is considered that there is a 
greater difference between complete suppression 
and the inhibition of all but one, or of all 
but two or three clamps, than between inhibi- 
tion of only about half the clamps. 
(3) The form of the anchors, as has been 
shown by Llewellyn (1957: Figs. 22 and 23 
for Gastrocotyle and Pseudaxine , and similarly 
in 1959: Figs. 8 and 9), is regarded as a 
generic character. The useful differences are 
the relative lengths of the handle (main root) 
and hook, of the spur (secondary root), and 
the approximate segment of a circle represented 
by the sickle-like hook. These characters are 
fundamental, since they are developed in the 
postlarval stages of the onomiracidium, and 
persist throughout life unless anchors are shed. 
The persistence of other larval anchors may be 
a specific character. 
(4) Additional sclerites associated with the 
penis, e.g., the peculiar forceps on the penis 
head. The only possible analogue is found in 
Heterapta Unnithan, 1961 (Heteromicrocotyli- 
dae), where the two spines appear to have a 
much deeper origin and are straight and much 
longer, probably functioning as vagino-dilators. 
(5) The occurrence of a single median 
dorsal vagina, or of paired vaginae opening 
laterally, at various levels, and their separate 
confluence into the lateral vitelline ducts, or 
the intervention of a median duct and, in some 
cases, the direct course of this to the ootype 
(as is more usual with an unpaired vagina) . 
(6) The relative size of the oral pouches 
and the pharynx (expressed as percentage of 
mean diameters), and the absolute size range 
of the latter and its shape. 
In view of the possibility of a wide array 
of related forms being discovered on tropical 
clupeoids in the future, I hesitate to give formal 
generic and specific definitions for these new 
forms, but prefer rather to list their diagnostic 
characters, with particular reference to the six 
criteria listed above, and other salient characters 
which appear taxonomically important in each 
case. 
Engraulicola micro pharyngella sp. nov. 
Figs. 1-6 
Four specimens of this new gastrocotyiine 
were collected from the gills of two mature 
female Anchoviella commersonii (Lacepe.) ex- 
amined at Trivandrum on August 14, 1957. 
All of the specimens except the one whole 
mount figured were broken while staining. The 
description is based mainly on this well pre- 
pared specimen (Fig. 1), but comparative 
measurements on the broken ones are also 
included. 
Body proper essentially bilaterally symmetri- 
cal, anterior and posterior ends narrower ; 
"neck” long and slender, about one-sixth of 
the total worm; haptor triangular with a short 
terminal lappet (Fig. 1). Total length 1.3-1. 9 
mm and maximum width 0.42-0.64 mm im- 
mediately in front of the ovary. 
Mouth subterminal and crescentic ; oral 
pouches thin-walled, spherical, 16-20 p, in diam- 
eter, opening into the buccal cavity; pharynx 
(unusually) smaller than oral pouches, spheri- 
cal and thin-walled, 14 p in diameter (ratio of 
oral pouch to pharynx = 130%) ; oesophagus 
