dcsimg

Description

provided by NMNH Antarctic Invertebrates

“Sub-genus Scleroconcha n. sub-gen. Philomedes (part.), autorum.

Diagnosis: — See above p. 380.

Remark: — For the number of species see above, p. 380.

Sub-genotype is Ph. (Scl.) Appelleifi n. sp.” (Skogsberg 1920, p.419)

“Maxilla: — End joint: The bristles of this joint, as will be seen from what has been said above, also show an exceedingly close agreement with regard to their position with the bristles of the corresponding joint in the sub-family Cypridininae. On account of this there can scarcely be any doubt that there is real homology present. In this case too I have thought myself justified in using a similar alphabetical notation, based on homologization, for these bristles as for those of the sub-family just mentioned. The group whose. (three to five) bristles form a transverse row on the outside of this joint are consequently denoted as a-bristles, the group (two) distally-anteriorly = b-bristles, the group (three to five) distally-medially = c-bristles and the remaining bristles, situated postero-distally on this joint = d-bristles.

Fifth limb: -- With regard to the homologization of the bristles on the second exopodite joint I merely refer to what has been written above in the description.

The classification of this genus.

Remarks: — The five species of this genus that have been described in this work certainly form quite a natural classificatory unit.

One of these forms, Ph. Appellofi, is, however, opposed to the others in some characters, especially by its strongly marked shell sculpture and its jointed rod-shaped organ. On account of this it seemed convenient to distinguish this species as a representative of a new sub-genus which has been, given the name of Scleroconcha.

Of the species of this genus dealt with in the literature it is rather certain that three others belong to this sub-genus, viz.:

Ph. Folini, G. S. BRADY, 1871, p. 294, pl. XXVII, figs. 1-5.

„ sculpta*’ “ “ “ 1898, p. 434, pl. XLIV, figs. 15-20.

„ flexilis, “ “ “ 1898, p. 435, pl. XLIV, figs.1-14, pl. XLV, figs.15, 16

* This species is, hesitatingly, identified by G. S. BRADY himself, 1898, p. 435 as Streptoleberis crenulata, G. S.BRADY, 1890, p. 515. This identification demands too much, however, from the inexactitude of the two descriptions to be adopted a priori. Of course its correctness is not absolutely impossible!! — It does not seem to me impossible that Ph. sculpta and Ph. flexilis are male and female of the same species.

All these three forms are characterized by a very powerful shell sculpture, developed in the form of extensive ridges. At least two of them, Ph. Folini and Ph. flexilis, have, in addition, a jointed rod-shaped organ of the same type as Ph. (Scl.) Appellofi. In Ph. sculpta, unfortunately, this organ is unknown. —It does not seem impossible that another species, Ph. Wyville- Thomsoni G. S. BRADY, 1880, p.160 pl. XXXVI, fig. 1, a - c, is to be referred to Scleroconcha too. Because of the incomplete description — this species is referred by G. W. MÜLLER, 1912, to “Cypridinidarum genera dubia et species dubiae" — nothing, however, can be said with certainty about it. .1

With regard to the mutual relations of the other species referred to this genus it is stuo too early to make any definitive statement; the descriptions are generally, unfortunately, too incomplete. It will probably be necessary — even after distinguishing Pleoschisma and Tetragond911 as special classificatory units, cf. p. 348 above — to carry out a further division; I need onilY, point out here that such aberrant forms as Ph. longiseta CH. JUDAY and Ph. lomae CH. JUDAY certainly cannot be retained in this genus.

Detailed diagnoses of the two following sub-genera may conveniently be postponed until a greater number of species of this genus have been subjected to a closer re-examination.” (Skogsberg 1920, p. 380)