. Bulletin of the British Museum (Natural History). 262 CP. NUTTALL. Fig. 294 Hebetancylus sp. Pebasian; Pichana, Peru; Hauxwell Colin. GG21570; specimen attached to fragment of bivalve shell, a, right hand side, x 50; b, apical view, x 50; c, front, x 100; d, rear, x 50. d'Orbigny Collection in BMZD, and no authenticated speci- mens from other sources are available for comparison in BMZD. Uncancylus (Pilsbry, 1914) (Recent, Brazil) is radially ribbed and has a pointed apex, whilst the Recent Peruvian Anisancylus (Pilsbry, 1924) is more tumid than Hebetancylus and its apex is situate
. Bulletin of the British Museum (Natural History). 262 CP. NUTTALL. Fig. 294 Hebetancylus sp. Pebasian; Pichana, Peru; Hauxwell Colin. GG21570; specimen attached to fragment of bivalve shell, a, right hand side, x 50; b, apical view, x 50; c, front, x 100; d, rear, x 50. d'Orbigny Collection in BMZD, and no authenticated speci- mens from other sources are available for comparison in BMZD. Uncancylus (Pilsbry, 1914) (Recent, Brazil) is radially ribbed and has a pointed apex, whilst the Recent Peruvian Anisancylus (Pilsbry, 1924) is more tumid than Hebetancylus and its apex is situated near the left margin of the shell. The present occurrence is thought to be the first definite fossil record of Ferrissiidae from South America. Parodiz (1969: 168) provisionally referred Ancylus humboldti Mayer Eymar (1900) from the ?Palaeocene of Chile to ?Palaeoancylus of the Ancylidae. Willard's (1966: 66) record of the brachio- pod Lingula in a Pebasian fauna from Negro Urea may possibly be based on a member of the Ferrissiidae, many of which can resemble Lingula in shape. The Ferrissiidae live in fresh water. Pilsbry (1914) recorded Gundlachia living on dead leaves and other debris on the bottom of pools. ?Hebetancylus sp. Fig. 294 Material studied. BMPD GG21570, Late Caenozoic, Pebasian; Pichana, Peru. Obtained from washings, 1982, from residues of Hauxwell Colin, 1870. No other records. Dimensions. 1, mm; br, mm; h, mm. Description. The shell is elongate oval and over twice as long as broad. It is comparatively low, with both the anterior and posterior slopes lying at about 30° from the horizontal. The apex is possibly rather worn and is smoothly rounded. It is situated not far behind mid-shell length and is bent, not very strongly, to the left. Traces of growth lines are visible only on part of the anterior slope. Remarks. The shell is not sufficiently well preserved to reveal any changes that may have occurred representing any post- ncanic metamorphosis
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