Mr. F. Smith on the Genus Centris. 357 Pholas crispata, L. Op. cit. iii. p. 112, v. pi. 53. f. 1. Abundant in the soft shale and sandstone at East and West Rocks, and especially opposite the castle. Sometimes the siphons are observed protruding through sand which coats some of the ledges, liouug specimens are often cast ashore on the West Sands in water-logged and decayed wood, whence they are extracted by the sea-fowl. Genus 3. Xylophaga, Turton. Xylophaga dorsalts, Turton. Op. cit. iii. p. 120, v. pi. 53. f. 4. Not common ; several living specimens occurred in the wood of a submerged thorn tree. Order Solenoconchia. Fam. DentaUdae, H. & A. Adams. Genus Dentalium, L, Dentalium entalis^ L. Op. cit. iii. p. 191, v. pi. 55. f. 1. Occurs on the West Sands in a living state after some storms. The specimens procured from the fishing-boats are generally tenanted by Sipunculi. Common. [To be continued.] XLIX. — A Revision of the Genera Epicharis, Centris, Eulema, and Euglossa, helonging to the Family Apidse, Section Sco-pulipedes. By Frederick Smith, Assistant in the Zoolo-gical Department of the British Museum. [Continued from p. 322.] Genus Centris. Centris (pt.), Fab. Syst. Piez. p. 354 (1804). TrrtcAina, Klug, lUig. Map. vi. p. 226(1807). Hemisia, Klug, ibid. p. 227 (1807). Ptilotopus, Klug, Berlin Mag. p. 32 (1810). Generic characters. Head not so wide as the thorax ; eyes large, lateral, elongate-ovate ; ocelli placed in a curve on the vertex ; antennse geni-
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