Proceedings of the United States National Museum . s two trifling concavities separated by a broaderconvexity. Between either antero-lateral angle and the posterior angle of thesame side, the outline presents a broad and shallow concavity which culminatesopposite the anterior part of the posterior row of plates of that interambulacralfield. The bottom of the test is not shown in the type, and the posterior borderis imperfect, so that the exact form of the latter and the exact position, etc.,of the peristome and periproct are unknown. Measurements.—Length of test, 10.); breadtli, 83; height (ap
Proceedings of the United States National Museum . s two trifling concavities separated by a broaderconvexity. Between either antero-lateral angle and the posterior angle of thesame side, the outline presents a broad and shallow concavity which culminatesopposite the anterior part of the posterior row of plates of that interambulacralfield. The bottom of the test is not shown in the type, and the posterior borderis imperfect, so that the exact form of the latter and the exact position, etc.,of the peristome and periproct are unknown. Measurements.—Length of test, 10.); breadtli, 83; height (approximately), 8-10 mm. AET. 20 A RARE CRETACEOUS SEA URCHIN REESIDE The writer believes tliat tlie genus ScuteUaster may fairly be regarded as a-synthetic, or generalized, type from which have been evolved Scutella on theone hand and Clypeaster on the other. In the present condition of the type, as shown by the retouchedphotograph forming figure 1 of plate 1, some of the details notedby Cragin are not evident. The ambulacral petals are entirely. < /of \t\ \
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Keywords: ., bookauthorun, bookcentury1800, bookdecade1870, booksubjectscience
