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Ren Xianqiu(Institute of Oceanology, Academia Sinica)  
Tetrachthamalus sinensis sp. nov. (Pl. 1.)Holotype 081073-1, diamter 4.7mm; Xinying, Hainan Island, Guangdong Intertidal, attached toTetraclita squamosa squamosa; Wang Yongliang coll. 1957. Ⅶ. 25. Paratypes C81073-2,3, 4,5. locality same as the holotype. Other materials examined About 35,000 individuals, from Hainas Island and Weizhou Island,Guangxi, attached to T. squamosa squamosa, (up to 7.0 mm in diameter).Shell small, conical, dirty white or grayish brown in colour, wall four plated, with strong ribs. Rostrum (concrescence of rostrum and lateral plates) rather broad, basal margin 2-4 times as broad as that of carina; radii narrow or obsolete, overlapping the laterals. Sutures between the coalesed rostral and lateral plates are distinct in the upper part of the plates, discernible from the outer surface of the rostral plate in eroded specimens. Sheath short, about one-third the height of wall plates. Surface below sheath smooth, basal margins of wall plates without inflected rim. Basis membranous.Tergum broad above, narrow below, articular ridge broad, articular furrow deep, spur short and broadly rounded, separated from the basi-scutal angle. Crests for lateral depressor muscle generally 3 in number. Scutum broadly triangular, wider than high; articular ridge straight, more than two-thirds the length of the tergal margin, lower end truncated, or slightly curved obliquely; adductor pit deep; lateral depressor pit deep and broad, with 1-3 lateral depressor crests.Labrum bullate, crest deeply concave, with more than a dozen of conical blunt teeth medially, lateral angles usually unarmed. Cutting edge of mandible with four teeth on upper portion, the fourth tooth (rarely 2nd-4th teeth) bifid; about 25-29 fine spines on lower pectinated portion, lower angle with a large tooth, followed by a small one. Cutting edge of 1st maxilla with 1 pair of strong spines and 3, 4 small ones on its upper portion, with 6-8 stout spines below the notch, its lower portion with several small spines.Terminal articles of both rami of the second cirrus provided with a few bidenti-culate setae (lanceolate spines), having serrate edges separated from the proximal first or second pairs of somewhat larger teeth.This new species differs from Tetrachthamalus oblitteratus Newman, the only species of the genus, in the presence of sutures on the upper portion of the composite rostral plate, in the labrum crest being deeply concave, in the cutting edge of the 1st maxilla being armed with 6-8 stout spines below the notch, and in the 2 rami of the 3rd cirrus being equal in length.
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