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Show 432 PROF. F. J. BELL ON THE ECHINOMETRIDsE. [Mar. 15, geographical distribution of the species than it has had hitherto; for the two specimens are both reported to have come from the island of Mauritius, whence the other species (P. indiana) has (as it seems) been already obtained ; and the only locality for P. granulata hitherto recorded is that of the Sandwich Islands. P. indiana has been received from {a) Masbate, (B) Philippine Islands, (c) Zamboanga (coll. Challenger), (d) Port Lincoln, Torres Straits. I do not find myself able to agree with the view according to which we should regard PseudoBoletia as standing in subgeneric dependence to Strongylocentrotus. It seems to me that, as defined by Prof. Troschel, it has the most distinct characters ; the constant possession of four pairs of pores, the deep gill-fissures and large gills, the constant abutting of two ocular plates on the anal region, the very considerable size of the lantern of Aristotle, are certainly enough characters which can hardly be subordinated to the form in which variability in the number of pores is found even in individual specimens, in which the gill-cuts are always slight, in which no ocular plate, or only one, may touch the anal area, and in which the buccal apparatus does not attain to any specially large size. But I need hardly attack this " man of straw ;" for although Prof. Alex. Agassiz does technically regard it as a subgenus, yet he (p. 455) speaks of it as a genus, and regards it as intermediate between the Echinometradse and the Echinidse. The size of the buccal apparatus is very remarkable : in two specimens of P. indiana, which had the test respectively 32 and 25 millim. high, the height of the lantern of Aristotle was 26 and 22 millim. respectively. If similar results should be obtained with P. granulata, it will be necessary to introduce the character into the diagnosis of the genus, and to examine into the extent of its affinity to Heterocentrotus. PSEUDOBOLETIA GRANULATA. Absolute diameter, in millim. 80 Percentage value of Height. 43-7 Actinostome. 36-2 Abactinal area. 15-6 Anal area. 6-8 |