Catalogue of the Marine Invertebrata of Eastern Canada

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1901 edition. Excerpt: ...that there is only one species ofMesodesma in Canadian waters, arid that the distinction between M. arctatum and M deauratum can scarcely be satisfactorily maintained. Young or not quite adult specimens, with the valves covered with a yellowish and sometimes slightly iridescent epidermis agree in that respect with the description of M. arctatum; whereas adult and aged specimens, with only a narrow strip of pale ashen gray epidermis around the ventral margin, correspond better with that of M. deauratum. Judging by the figures in the second edition of Dr. Gould's Invertebrata of Massachusetts, the principal difference between these two forms would seem to be that in M. arctatum the short posterior end is so abruptly subtruncate that the beaks are almost terminal; whereas in 31. deauratum the same part of the shell is somewhat produced. In this particular, all the Canadian specimens that the writer has seen, agree better with the figure of M. arctatum than with that of M. deauratum. In a letter dated Feb. 18th, 1901, Dr. Dall writes as follows on this point. In regard to the Mesodesmas Stimpson recognizes three forms: deauratum, Turton (1822) more rounded. flattened. longer and more angular. yellowish. thin. do. Radial lines obvious. Shell broad. obsolete. broad. narrower. I am not dogmatic about them, but would be disposed to recognize two, at least, one turgid and short in front, the other flatter and longer. They are very close to each other at best, and all found in the Gulf of St. Lawrence. Family Serobiculariidce. Cumingia Tellinoides (Conrad). Mactra tellinoides, Conrad (1831). Cumingia tellinoides, Holmes (1859); Verrill (1875). Prince Edward Island, only one specimen seen (Sir J. W. Dawson, 1871); south...