. Bulletin of the British Museum (Natural History). 192 CP. NUTTALL. Figs 66-67 Dyris tricarinata (Boettger). Pebasian; Pichana, Peru; Hauxwell Colin. 66, G25289; a, oblique view of apertural region, x 30; b, oblique view of apex, x 66; see also Fig. 63. 67, GG21692; oblique view of apex, x 50. Description. The apex consists of 2-2'/2 biconvex whorls which rapidly increase in size, and are smooth except for opisthocyrt growth lines. Spiral sculpture of sharp, coarse ridges or carinae quickly develops and, in the next whorl or so, these strengthen to superimpose the very variable but
. Bulletin of the British Museum (Natural History). 192 CP. NUTTALL. Figs 66-67 Dyris tricarinata (Boettger). Pebasian; Pichana, Peru; Hauxwell Colin. 66, G25289; a, oblique view of apertural region, x 30; b, oblique view of apex, x 66; see also Fig. 63. 67, GG21692; oblique view of apex, x 50. Description. The apex consists of 2-2'/2 biconvex whorls which rapidly increase in size, and are smooth except for opisthocyrt growth lines. Spiral sculpture of sharp, coarse ridges or carinae quickly develops and, in the next whorl or so, these strengthen to superimpose the very variable but basically bicarinate adult whorl profile upon the biconvex smooth profile of earlier whorls. Perhaps the most constant feature is the ramp which occupies virtually all the adapical half of the whorl and slopes steeply at 60°-70°. In some specimens from La Tagua the spiral ribs are more numerous but weaker, so that the profile reverts to biconvex for the last whorl or so. In a small proportion of shells from Pichana the spiral carinae are of irregular strength, giving a slightly frilly appearance. The peristome is rimmed and sometimes slightly detached. Dimensions. In mm. h br hap h/br sa Lectotype, Pebas (from de 21° Greve, 1938) G25289, Pichana 22° G25290, Pichana 45° GG19936, La Tagua, 25° 33/480-560 cm GG19840, km upstream from 28° La Tagua GG 19841, as above. 28° GG 19842, as above. 4 1 25° GG21528, Puerto Narino. 26° GG21527, Puerto Narino. 26° Remarks. De Greve (1938), when designating types, refigured Boettger's (1878) type material from Pebas, but none of his own from Iquitos. De Greve's measurements are highly suspect: he gave two views of the lectotype at different magnifications, but neither agrees with the dimensions that he gave (1938: 83) in his text and which are quoted here. Conrad thought that this species was the y
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