Smithsonian miscellaneous collections . ral plates which would normally beadjacent to this ambulacrum. Ontogeny.—The ambulacral lunules are not present in the smallestspecimen, mm long (text fig. 38), but there are slight marginalnotches in ambulacra II and IV and more developed notches in Vand I. In a specimen mm. long (text fig. 39) there are deepnotches in the paired ambulacra, with the notches in ambulacra IIand IV almost closed, and in a specimen mm long (text fig. 40) NO. 5 TERTIARY ECHINOIDS FROM FLORIDA—KIER 43 there are lunules in all the paired ambulacra. A lunule in a
Smithsonian miscellaneous collections . ral plates which would normally beadjacent to this ambulacrum. Ontogeny.—The ambulacral lunules are not present in the smallestspecimen, mm long (text fig. 38), but there are slight marginalnotches in ambulacra II and IV and more developed notches in Vand I. In a specimen mm. long (text fig. 39) there are deepnotches in the paired ambulacra, with the notches in ambulacra IIand IV almost closed, and in a specimen mm long (text fig. 40) NO. 5 TERTIARY ECHINOIDS FROM FLORIDA—KIER 43 there are lunules in all the paired ambulacra. A lunule in ambula-crum III is present in a specimen mm long (text fig. 41). Comparison with other species.—This species is distinguished fromall the other species of the genus in having in adult specimens fiveinstead of four ambulacral lunules. Remarks.—Previously all species of the Mellitidae having fourgenital pores and five ambulacral lunules have been referred toLeodia. Although this species has five ambulacral lunules, it has all. Fig. 37.—Mellita aclinensis Kier, new species: Adapical view of abnormalspecimen 648193, from the Tamiami formation, loc. 27, X 3. the other characters of Mellita that distinguish this genus fromLeodia (see table 4). Therefore it seems reasonable to considerthis a species of Mellita, and to broaden the generic concept of thegenus to include species having five ambulacral lunules. Durham (1961, p. 3) predicted that Mellita would be found inthe Miocene and Pliocene of the Neotropical region: In view ofits occurrence only in the tropical and warm temperate areas of thewestern Atlantic and eastern Pacific, it is evident that Mellita musthave a fossil record extending back to at least the upper Miocenewhen the Central American seaways were open (Durham and Alii- 44 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I45 Table 4.—Characters distinguishing Mellita from Leodia Mellita Four ambulacral lunules *Posterior lunule extending far ante-rior
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