. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. 20 Bulletin Museum of Comparative Zoology, Vol. 150, No. 1 pedal retr. mus visceral ganglion post. add. mus. hind gut siphon. tentacle palp proboscis ant. add. nnus. pedal ganglion ant. sense organ cerebral ganglion palp , / , foot byssal gland 1 mm Figure 17. Spinula scheltemai. Semidiagrammatic view of the right side of animal to show disposition of organs. (Fig. 19). The siphon is not obviously a double structure of the type figured by Yonge (1939). It is internally ridged. The mid-lateral ridges, continuations of
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. 20 Bulletin Museum of Comparative Zoology, Vol. 150, No. 1 pedal retr. mus visceral ganglion post. add. mus. hind gut siphon. tentacle palp proboscis ant. add. nnus. pedal ganglion ant. sense organ cerebral ganglion palp , / , foot byssal gland 1 mm Figure 17. Spinula scheltemai. Semidiagrammatic view of the right side of animal to show disposition of organs. (Fig. 19). The siphon is not obviously a double structure of the type figured by Yonge (1939). It is internally ridged. The mid-lateral ridges, continuations of the gill attachment, are somewhat more ob- vious than the others. Faecal rods are confined to the dorsal side of the lumen, and probably the internal ridging effec- tively divides the siphon in two. Dorsal- ly, the siphon is attached by connective tissue that passes postero-lateral to the hind gut. The gut takes the usual course. Here the mid gut and hind gut penetrate some distance into the foot ventral to the large pedal ganglia. There are 10 coils on the right side of the body, although in most specimens there appear to be only 8. However, sections and whole mounts show that two of the coils may be hidden internal to the tightly packed outer coils. The stomach is large and displaced far to the left side of the body (Fig. 18). The foot and the 'byssal' gland are well developed. The pedal retractor muscles are similar to those described for S. fi- latovae (p. 7). There is a change in shape with in- creasing length (Fig. 20). As in other species, increasing prominence of the rostrum results in a change in position of the umbo relative to the total length. In some cases (Fig. 21) the umbo is poste- rior to the midline. Total length with re- spect to height changes but little during the growth of the animals. The smallest specimen showing gonadal development was mm total length. Sexes are sepa- rate with the larger animals tending to be more mature. No specimen appeared to. P
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