REPORT ON THE LAMELLIBRANCHIATA. 135 



Cytherea [Callista) disrupta, Sowerby (PI. I. figs. A-Ae). 



Cytherea disrupta, Sowerbj-, Thcs. Conch., vol. ii. p. 74.3, pi. clxiii. figs. 208, 209. 



Testa transversim eloHgato-ovalis, postice subacuminata, modice convexa, valde 

 insequilateralis, nitida, concentrice tenuissime striata, incrementique lineis sulciformibus 

 et liriformibus oriiata, sub epidennide tcnui, alba roseo-fusco copiose subradiata, irregu- 

 lariterque maculata, in dorsum postice maculis saturatioribus magnis tres vel quatuor 

 irregularibus picta. Margo dorsalis posticus elongatus, aliquanto convexus, oblique 

 descendens, anticus paulo concavus, declivis, multo brevior. Ventris margo incrassatus, 

 late curvatus, aiitice loiige adscendens. Lunula ovato-lauceolata, coucava, plerumque 

 alba, linea incisa circumscripta. Umbones mediocres, parum elevati, circiter in \ longi- 

 tudinis coUocati. Pagina interna alba, umbones versus macula magna livido-purpurea 

 tincta. Cardo dentibus approximatis. Sinus pallii profundus, latir.sculus, ad apiccm 

 oblique truneatus, angulo terminali acuto. 



Xhe form of this species is transversely long oval, ratlier more acuminate behind 

 than in front. The dorsal margin is elongate, somewhat arched and oblique posteriorly, 

 the anterior portion being less than half the length of the posterior side, more sloping 

 and concave. The lower outline is widely arcuate, and rather more ascending in front 

 than behind. The shell is moderately convex, very inequilateral, finely concentrically 

 striated, and exhibits rather coarse lines and grooves of growth, especially in adult shells, 

 which do not, however, affect the dorsal area. Beneath a very thin epidermis it is 

 whitish, copiously stained and blotched irregularly with a pinkish-brown colour, generally 

 in a more or less subradiating manner, and upon the hinder dorsal area, and in front of 

 the lunide, it is ornamented with a few large darker blotches. The lunule is concave, 

 generally white, or with perhaps one or two small dark brown specks upon it, of an 

 ovate-lanceolate form, and enclosed by a fine impressed line. The umbones are small, 

 a little raised above the hinge-line, rosy at the apices, and situated at a little more than 

 a quarter of the whole length from the front end. The interior is white at the sides 

 and lower margins, which are rather thickened, but from the centre to the beaks is 

 .stained wath a livid purplish tint, which in full-grown specimens is more or less concealed 

 by callus. The hinge is rather slight and composed of fine approximated teeth. The 

 sinus in the pallial line is wide and rather deep, but not reaching quite to the centre of 

 the valves. It is obliquely broadly truncated at the end, the upper angle being 

 rounded and the lower rather acute. 



The dimensions of half-grown specimens are — length 26 mm., height 18, diameter 

 11|. Adult examples are 41 mm. in length, 32 high, and 21 in diameter. 



Habitat. — Port Jackson, New South Wales, in 2 to 10 fathoms. 



There are two or three species with which this is likely to be confounded, namely, 



