. Bulletin - United States National Museum. d the same numbers respectively in theinterambulacra, Both specimens have only three plates in a series onthe peristome, The tridentate pedicellariae are characteristic in having a distinctarc under the articular surface (fig. 3, a), a character otherwise knownonly in Sperosoma durum Doderlein. In the smaller specimen there REPORT ON THE ECHINOIDEA MORTENSEN 13 are numerous ophicephalous pedicellariae (fig. 3, d) also resemblingthose of S. durum. In the larger specimen only a single ophicepha-lous pedicellaria was found, which looks rather different
. Bulletin - United States National Museum. d the same numbers respectively in theinterambulacra, Both specimens have only three plates in a series onthe peristome, The tridentate pedicellariae are characteristic in having a distinctarc under the articular surface (fig. 3, a), a character otherwise knownonly in Sperosoma durum Doderlein. In the smaller specimen there REPORT ON THE ECHINOIDEA MORTENSEN 13 are numerous ophicephalous pedicellariae (fig. 3, d) also resemblingthose of S. durum. In the larger specimen only a single ophicepha-lous pedicellaria was found, which looks rather different (fig. 3, b) —not like those of S. durum. The smaller specimen is a beautiful purple, the larger a lightgrayish. These two small specimens cannot with certainty be referred to anyof the species known from the Malay Archipelago. It can only beseen with certainty that they belong to the genus Sperosama, sincesome of the oral ambulacral plates are divided into two in the waytypical of this genus. It is not very likely that both belong to one. 3.—Valves of pedicellariae of Sperosoma sp., young: a-c, Specimen from station5608; d, specimen from station 5332. a, Valve of tridentate pedicellaria ; possibly theedge of the blade not yet fully developed (without serrations) ; b and d, Valves ofophicephalous pedicellariae; c, valve of triphyllous pedicellaria. All X 80. and the same species, in spite of the fact that both have the peculiararc under the valves of the tridentate pedicellariae; the differentshape of the ophicephalous pedicellariae would seem to preclude theidea of their belonging to the same species. That one of them maybe identical with S. durum is quite possible; but the fact that thesmall specimen, the ophicephalous pedicellariae of which resemblethose of S. durum,, has the fewer number of aboral ambulacral plates,whereas S. durum has, when adult, about three times as many aboralas oral ambulacral plates, is not in favor of such identity. ThatS. durum is known h
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Keywords: ., bookauthorun, bookcentury1800, bookdecade1870, booksubjectscience
