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I am somewhat doubtful about the homologization of the masticatory pad and the oval
cavitv on the pars incisiva on the coxale in this genus. Does the masticatory pad in this genus
correspond to the masticatory pad -j- the part surrounded by the bristles and hairs or only
to the former in the genus Conckoecial And in the latter case does the part surrounded by the
bristles and hairs in the latter genus correspond to the oval cavity in Euconchoecia ? It does
not seem possible at present to answer these questions with füll certainty.
Euconchoecia Chierchiae G. W. Müller.
? Euconchoecia Chierchiae, G. W. Müller, 1890 a, p. 277; pl. XXVIII, figs. 1—10.
Paraconchoecia oblonga, P. T. Cleve, 1900, p. 40.
Euconchoecia Chierchiae, G. S. Brady, 1902 a, p. 190; pl. XXIV, figs. 9—15.
? „ „ (part.), G. W. Müller, 1912, p. 96.
Description: — Male: —
Shell: — Length, 1,15—1,25 mm. Length :height about 2:1; length :breadth about
2,3 : 1. Seen from the side (fig. 1), it is moderately elongated, with its greatest height
somewhat in front of the middle and the anterior part of the shell somewhat, thougli rather
slightly, larger than the posterior part. The ventral margin is moderately strongly and uniformly
curved and passes without corners into the anterior and posterior margins. The posterior
margin is also uniformly and moderately curved; it forms an angle of about 90° with the dorsal
margin. At the posterior dorsal corner the right valve is in most cases* armed with a moderately
long, narrow spine, more or less pointed distally. The left valve is more or less rounded liere,
armed in most cases with a very small spine (fig. 4) ; the latter is sometimes quite absent, however
(as in fig. 8 of the female) ; in exceptional cases (cf. p. 754 below) botli valves have a well developed
spine in this corner. The rostrum points almost straight forward; it is rather broad and
symmetrica! (fig. 5). The shoulder vault is rather small, well rounded, not wing-shaped. S e e n
from below (fig. 2), the shell is somewhat lentil-shaped, with its greatest breadth somewhat
in front of the middle and its anterior part distinctly larger than the posterior part; it is rather
broadly rounded anteriorly and grows narrow rather rapidly posteriorly, where it becomes
pointed; the side-contours are rather evenly curved. In the specimens investigated by me
the surface of the shell had no perceptible sculpture and no hairs. There are no
signs of a hinge-socket or a hinge-tooth postero-dorsally. Seen from inside: The
selvage* is very narrow and extremely difficult to verify with certainty; as far as I could
observe it had a whole margin throughout its length, even on the rostrum. The lamellae of
the shell are exceedingly thin; the part at which they are joined is narrow.
First antenna (fig. 12): — The first joint has disto-ventrally a rather large,
verruciform, rounded process. (A process of about the same kind is found in all the males of this
genus in which this antenna is known; is it a generi c character?) The fourth joint has ventrally
somewhat more than twenty (21—24 found) sensory bristles, arranged in three longitudinal
* Ct. the remark on this species, p. 752 below.
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