88 THE VOYAGE OF H.M.S. CHALLENGER. 



Semele (Abra) longicallus (Scacclii). -"^ 



TeJlina longicallus, Scacclii, Notizie Concli. foss. di Gravina, itc, p. 16, \>]. i. fig. 7. 

 Erycina longicalUs, Philippi, Euum. Mol. Sicil., vol. ii. p. 9, pi. xiii. fig. 7. 

 Alira loiifficall is, Sars, Moll. Eeg. Arct. Norv., p. 74, pi. vi. figs. 3a-c, pi. xx. fig. 4. 

 Syntlosmija longicalUs, Dall, Bull. Mus. Comp. Zool., Harvard College, vol. ix.. No. 2, p. 133. 

 Scrohicularia loiigicallns, Jetfrej'S, Proo. Zool. Soo. Lond., 1881, p. 926. 



Habitat. — Station 75, off the Azores, in 450 fathoms ; volcanic mud. 



For the distribution of this species, which occurs in many phices, and at vastly 

 different depths in the Atlantic, and also in a fossil state in Italy and Norway, reference 

 should be made to the paper by Dr. Gwyn Jeffreys quoted above. 



Semele [Abra) j^rofunclorum, n. sp. (PI. Y. figs. 5-56). 



Testa leviter iufequilateralis, transversim ovato, postice hians valdeque acuminata, 

 subcompressa, tenuis, subdiaphana, alba, polita, conceutrice exiliter striata, antice 

 anguste lunulata, postice area lineare instructa. Umbones ^ arvi, acuti, paululum pone 

 medium siti. Margo dorsalis posticus obliquissimus, subrectus, anticus prope umbones 

 leviter concavus, deinde vix excurvatus. Dentes cardinales duo in utraque valva, valde 

 intequales. Sulci laterales in dextra angusti, profundi, ab apice subremoti. Fossa pro 

 ligamento angusta, elongata. Impressiones musculares insequales, antica elongata, postica 

 rotunde pyriformis. Sinus pallii latus, profundissimus. Fascies valvarum interna 

 plerumque polita, seel in medio, umbonesque versus minutissime subgranulata. 



This sjjecies is longer than high, broadly rounded in front and ratlier acuminate at 

 the hinder end. The shell is inequilateral, the anterior portion being rather the longer, 

 very thin, transparent, ami moderately flat and slightly gaping posteriorly. The surface 

 is smooth and glossy, and sculptured with fine concentric strife or lines of growth, and in 

 addition faint indications of very unimportant radiating sculpture are traceable. The 

 hinder dorsal slope descends very obliquely, and is almost rectilinear. The anterior 

 margin is much more horizontal and slightly arcuate, except close to the umliones, where 

 a faint conca\"ity is met with. The lunule is elongate, narrow, and defaced by a slight 

 but distinct ridge on each side. The area is also narrow and defined by a sharpish ridge 

 on each valve extending just beyond the lateral teeth. In addition to this there is a 

 second but less acute angle on each A'alve, forming, as it were, a second larger area 

 reaching to the posterior extremity of the shell. The beaks are small, acute, and 

 a little elevated. The cardinal teeth are two in number in each valve. In 

 the right the posterior is twice as large as the front one, whilst in the left it is 

 smaller, thin, lamellar, and borders the cartilage-pit. The lateral dental grooves in the 

 dextral valve are narrow, deep, and moderately distant from the umbo, which they 

 do not reach on either side. The internal ligament-pit is long and narrow, and parallel 



