Cross-checking of the original material and labels for Philobrya brattstromi with the data from Soot-Ryen's publications (1957, 1959) confirms that that author had designated a holotype and five paratypes by 1953. All specimens other than those from station M24 and determined in the same year are thus excluded from the type series. The correct height of the holotype is 5.5 mm and not 15 mm as originally indicated by Soot-Ryen (1957) or 5.8 mm as he indicated subsequently (Soot-Ryen, 1959). The prodissoconch of P. brattstromi is devoid of sculptural elements (also at high magnifications) except for a raised, round-crested shell margin as already described by Soot-Ryen. However, it also has an incipient dorso-central boss and well-developed anterior and posterior wings. The mean length is 627 μm; the I/II ratio of 1.5 is high when compared to eleven congeners for which such measurements are available. Prominent morphological features of the postlarval shell are: (1) well-developed posterior G1 teeth which considerably increase in length antero-ventrally to a elongated ligament and that disintegrate ventrally into pustules; (2) four to five posterior tooth-like folds on the inner margin (previously described by Soot-Ryen), which correspond in number with ribs on the outer surface of valve; (3) a non-flaky periostracum. The shell microstructure is linear to complex crossed-lamellar with an inner prismatic layer. The additional presence of a (vestigial?) outer prismatic laver dorsal to the ligament area, the pustular disintegration of G1 teeth and the presence of a dorso-central boss on the prodissoconch resemble these states in the Limopsidae. However, it remains questionable whether these traits are inherited or convergent.
|Publication status||Published - 30 May 2006|