REPORT ON THE LAMELLIBRANCHIATA. 219 



the left. The lateral teeth arc distinct on both sides, tlie anterior in the richt vnlve and 

 tiie posterior in the left being separated from the outer margin by a deepish groove, the 

 posterior in the former and the front one in the latter being, on the contrary, on the margin. 

 The hinge-plate between the cardinal and lateral teeth is seen under the microscope 

 to be finely transversely striated, and the outer margin is strongly dentate within. 



Length 2f mm., height 2§, diameter 2. 



Habitat. — Station 188, south of New Guinea, in 28 fathoms; green mud. 



This species is remarkable for its small size and the crowded transverse tubercles on 

 the radiating costse, which are separated by very narrow liut deep intervening grooves. 



Family C K A s s a t e l l i d .^. 

 Crassatella, Lamarck. 



Crassatella aurora, A. Adams and Angas. 



Crassatella aurora, A. Adams and Aiigas, Piiju. Zool. Soc. Loud., 1863, p. 426, pi. xxxvii. fig. 15. 



Habitat. — Station 1G2, off East Moncceur Island, Bass Strait, in 38 fathoms; sand 

 and shells. 



The types of this species, liberally presented to the British Museum by G. F. Angas, 

 Esq., were collected at Banks Strait, Tasmania. They are rather more finely ribbed 

 than would appear to be the case judging from the figure. The Challenger .specimens, 

 which are all smaller than the shell figured, have, however, coarser ribbing, the ribs 

 being attenuated laterally and scarcely reaching to the dorsal margins. The two 

 interrupted brownish rays appear to be a constant character, and the interior exhibit.s 

 more or less of a delicate rose colour. The hinge-plate on both sides of the cardinal 

 teeth is also rose-tinted, and the inner edsre of the valves alono- the ventral margin is 

 finely crenulated. 



Crassatella rhomboides, n. sp. (PI. XVL figs. 1-la). 



Testa compressa, quadrata, albida, vel pallide rufescens, valde insequilateralis, 

 concentrice subdistanter tenuiter lamellato-costata, striis micro3co])icis interruptis 

 concentricis undic|ue sculpta. ]\Iargo dorsi posticus subhorizontalis, rectus, elongatus, 

 anticus abrupte obliquus, subperpendicularis, rectilinearis. Margo ventralis vix curvatus, 

 dorsali postieo subparallelus. Latus anticum inferne rotunde angulatum, posticum 

 truncatum, supra et infra subrecte angulatum. Umbones parvi, acutissimi. ad apicem 

 conico-producti, partem anticam versus coUocati. Dentes cardinales graciles, elongati. 

 Margo valvarum internus inferne denticulatus. 



