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Lithomelissa cheni Caulet, 1991

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Description. Smooth two-segmented shell, cephalis smaller than the thorax. Apical spine free in the inner part of the cephalis, protruding outward as a stout apical horn shorter than the thoracic length. Vertical spine thin, extending through the cephalic wall as a short, three-bladed vertical horn, in the plane of the collar stricture. Lateral and dorsal spines extend for a short distance inside the upper part of the thoracic wall forming small shoulders. No external prolongations. Small subcir- cular pores. Collar stricture distinct. Thorax wider than the cephalis, smooth. Termination always ragged.
Remarks. The main differences between this species and L. ehrenbergi were observed by Chen (1975): "... differs in having a longer thorax and in the absence of exposed dorsal and two lateral spines." The illustration published by BŘtschli (1882) is not clear about the lateral and dorsal spines, but his synonymy with the specimen described by Ehrenberg (1875, pi. 3, fig. 8) shows that L. ehrenbergi must possess strong external lateral and dorsal spines. L. cheni is also distinguished from L. ehrenbergi by a prominent horizontal vertical spine.
Name. In honor of Pei-Hsi Chen who first described this species.
Occurrences. The FCO is in Sample 119-738B-3H-6, 53-55 cm (early Oligocene). The LCO was not observed in Leg 119 material. The LCO is in the middle Miocene at DSDP Site 594 (Chatham Rise, south of New Zealand).
Dimensions. Length of apical horn: 20-40 Ám; of vertical spine: 10- 15 Ám; of cephalis: 60-65 Ám; of thorax: 85-95 Ám. Maximum breadth of cephalis: 55-62 Ám; of thorax: 60-75 Ám.
Types. Holotype (MNHN no. F61380), Sample 90-594-52-2, 84-86 cm, 1-R42/3 (PI. 2, Fig. 1). Paratype (MNHN no. F61381), Sample DSDP 90-594-52-2, 84-86 cm, 2-B50/3 (PI. 2, Fig. 2).
Caulet 1991


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