. Bulletin of the British Museum (Natural History) Zoology. . Fig. 63 Ledella ultima: (a) Right lateral external view of the Holotype specimen (BMNH No. ) (note margin not thickened); (b) internal view of right valve of specimen with thickened margin from Station 175. (Scale = 1 mm). well developed, the inner fold being moderately broad. The combined siphon is not fused ventrally and is fairly small. A very fine siphonal tentacle, often difficult to observe, is attached close to the base of the siphonal embayment on the right or the left side. The anterior sense organ is more vent
. Bulletin of the British Museum (Natural History) Zoology. . Fig. 63 Ledella ultima: (a) Right lateral external view of the Holotype specimen (BMNH No. ) (note margin not thickened); (b) internal view of right valve of specimen with thickened margin from Station 175. (Scale = 1 mm). well developed, the inner fold being moderately broad. The combined siphon is not fused ventrally and is fairly small. A very fine siphonal tentacle, often difficult to observe, is attached close to the base of the siphonal embayment on the right or the left side. The anterior sense organ is more ventrally situated than in other species. The adductor muscles are large, approximately equal in size and round in shape. The gills lie parallel to the posterior dorsal margin with 8-11 gill plates. The labial palps are large with 14-20 ridges and with long, thin palp proboscides. The foot is large, deeply cleft with a very large 'byssal' gland (Fig. 68). The stomach and style sac lie ventral to the umbos, they are relatively small, extending only into the upper third of the foot, posterior to the pedal ganglion. From the style sac the hind gut passes posterior and ventral to the pedal ganglion before retracing its path to the dorsal margin and then to the right side of the body where it forms a series of coils. These usually number 12 although exceptionally 13 have been observed. One individual was also observed with an additional loop to the left side of the body. The coils are stacked in an overlapping sequence dorsally and antero-laterally to the vis- cera. Some coils lie internal to the others, thus, a variable number of coils is immediately visible in lateral view, the most common number being eight. The extent of the area covered by the coils also varies, depending on the compactness and shape of the coils, which may be circular or oval in Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - co
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