REPORT ON THE LAMELLIBRANCHIATA. 177 



The anterior muscular impression which falls within the pallial line is narrow, elongate, 

 and oblique. 



Length 15 mm., height 14, diameter 9. Another specimen in the British Museum is 

 16| mm. long and 16 high. 



Habitat. — Cape York, North Australia, in 3 to 12 fathoms. 



There is only one other species with which this is likely to be confounded, namely, 

 Lucina macandrerp, H. Adams, from the Gulf of Suez, which maybe the same species as 

 Lucina ornatissima, d'Orbigny, hereafter referred to. That species has the umbones 

 more elevated, the lunule a little larger, the single tooth in the right valve bigger, and 

 the anterior muscular scar much broader. But another and perhaps the most important 

 distinction is found in the divaricating ridges. These in Lucina macandrete are a trifle 

 more slender, granular or serrated along the top, and divaricate at an angle of about 25° 

 at the central part of the valves. On the contrary, in Lucina irpex the angle of 

 divergence is much less acute, being about 45°, and the costellse themselves, although 

 somewhat rugose, are not serrated in the same manner. Lucina ornata, Reeve, is 

 another allied species, difi"ering from the two previously mentioned in having the 

 divaricating ridges less elevated, broader and flat-topped, the upper edges of them being 

 somewhat raised and carinate. The angle at which they diverge is about the same, 

 namely 45°, as in Lucina irpex. This species [Lticina ornata) has since been described 

 by Dr. E. von Martens^ under the name of Lucina (Divaricella) angidifera from 

 specimens collected at the Mauritius. In the British Museum there are three specimens 

 obtained by Captain Owen, R.N., on the coast of Africa, and others collected by 

 J. B. Jukes, Esq., at Port Jackson, New South Wales. The type-shell figured by Reeve 

 (Conch. Icon., fig. 48) is a little abnormal in form, the anterior side being unusually sloping 

 at the upper part, but not excavated at the lunule as represented in the figure. 



Lucina {Cyclas) cumingii, Adams and Angas, is the largest species of the section 

 Divaricella, and is found in Ceylon, South Australia, Tasmania, Port Jackson, and New 

 Zealand. It should certainly be held distinct from the West Indian Lucina dentata, 

 [Wood * = ZifciHtt divaricata, Auct. {non hinn.) = Lucina serrata, d'Orbigny = Z^<cina 

 chemnitzii, Philippi = ZwcM7a strigilla, Stimpson (probably)]. It difl"ers from that species 

 in being larger in the adult state, has more acutely divaricating strife, a more elongate 

 lanceolate lunule, a more external ligament, and a single lateral denticle in each valve on 

 the anterior side, moderately remote from the cardinal teeth, of which there is not the 

 slightest trace in Lucina dentata. The front muscular scar, too, is much more elongate, 

 and the margin of the valves is never serrated, but perfectly smooth. 



Care must be taken not to confound the two West Indian forms Lucina dentata and 

 Lucina quadrisulcata, which has also been named by C. B. Adams Lucina americana. 



1 Mollusca dor Insel Mauritius, p. .321, pi. xxii. fig. 14. 

 ^Tellina dentata, Wood, General Concli., p. \^5, \)\. xIfL fig. 7. 

 (ZOOL. CDALL. EXP. — PAKT x.x.\v. — 1885.) Mm 23 



