Bulletin of the Museum of Comparative Zoology Volume 64

Paperback | May 5, 2014

byThomas Augustus Bland, Harvard University Zoology

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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. 1921 edition. Excerpt: ...Russian Onchometopus they are probably not congeneric with it. The two genera form one more example of that "Parallelism among the Asaphidae" to which I have already called attention (Trans. Royal soc. Canada, 1912, 6, sect. 4, p. 111). Detailed study with large numbers of specimens indicates that Onchometopus is a derivative of Asaphus, while Homotelus sprang from Isotelus, not once merely, but probably several times. Homotelus differs from Isotelus chiefly in lacking the concave borders on the shields. Often specimens are found in which concave borders are feebly or sometimes even well developed, indicating that this characteristic is one of suppression and showing readily how a Homotelus could have been evolved time after time from various species of Isotelus. Homotelus cannot then be regarded in a strict sense as a good genus, but is a convenient term for a number of species showing similar characteristics. At the time of our first use of Onchometopus, Mr. Narraway and I pointed out that the American species which we referred to the genus did not have the peculiar hooked doublure which Schmidt considered the most important feature. In 1914 it was my privilege, aided by the Shaler Memorial fund, to collect Onchometopus from the typical localities south of Lake Ladoga, and direct comparison of specimens is now possible. Cephala of American and Russian forms are exceedingly alike in smoothness of glabella, position of eyes, course of facial sutures, and shape of fixed and free cheeks. Doublures are strikingly different not only in the hooked and furrowed character of the Russian form, but also in its narrowness. Greater differences are seen in the thorax, where Onchometopus shows the high narrow rings of an Asaphus while the Homotelus...

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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. 1921 edition. Excerpt: ...Russian Onchometopus they are probably not congeneric with it. The two genera form one more example of that "Pa...

Format:PaperbackDimensions:172 pages, 9.69 × 7.44 × 0.37 inPublished:May 5, 2014Publisher:General Books LLCLanguage:English

The following ISBNs are associated with this title:

ISBN - 10:0217963250

ISBN - 13:9780217963251

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