. The Conchologists' exchange. Mollusks. 2 THE NAUTILUS. on the under side of stones on a coarse, pebbly beach, and here it still retained its characteristic, long, narrow form. See Proceedings of Boston Society of National History, Vol. 32, No. 2, Nov., 1904. All the illustrations here are of the same magnification. In the fifteen specimens of Acmaea testudinalis collected and studied the radulas were all the same with no observed variation, see PI. II, Fig. 1. All had two central (C C), two lateral (L L), and two outermost teeth (U U), while among the thirty A. alveus were several abnormal r
. The Conchologists' exchange. Mollusks. 2 THE NAUTILUS. on the under side of stones on a coarse, pebbly beach, and here it still retained its characteristic, long, narrow form. See Proceedings of Boston Society of National History, Vol. 32, No. 2, Nov., 1904. All the illustrations here are of the same magnification. In the fifteen specimens of Acmaea testudinalis collected and studied the radulas were all the same with no observed variation, see PI. II, Fig. 1. All had two central (C C), two lateral (L L), and two outermost teeth (U U), while among the thirty A. alveus were several abnormal radulas, in all of which abnormal cases there were three teeth in the center, PI. II, Fig. 4, instead of two, PI. II, Fig. 2, which is the normal number for alveus. The additional or third tooth (A), see PI. II, Fig. 4, is on the left side and is a narrower tooth than the other two (C C). These abnormal radulas came from three very different individuals: one from a large, blackish, distorted shell, an adult, and one from a small, regular, white specimen of the nepionic age, and so on, all being different. There are several differences between the radulas of testudinalis and of alveus^ and these differences were constant throughout the speci- mens examined. Fig. 5. Fig. 6. Fig. 5 (in text). Acmaea testudinalis (Miill). Normal adult rad- ula. Developing teeth of the posterior portion of the same radula as Fig. 1. Lettering the same. Fig. 6 (in text). Portion of anterior part of radula of Acmaea tes- tudinalis, showing small bases (B), proximal portion of cusp (P C),. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Averell, William D. Philadelphia, Wm. D. Averell
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectmollusks, bookyear188
