167 



greater development of costse and the less defined granular orna- 

 ment, and by the last whorl being conspicuously spirally sulcated 

 throughout. 



3. Semicassis Muelleri, spec, nov, Plate vii., fig. 9, 



Shell rather thin, globosely inflated; spire short, ending in a 

 small pullus of one and a half, smooth, slightly swollen whorls. 



Whorls four, excepting pullus, separated by an impressed 

 suture, roundly angled medially, spirally ribbed ; the posterior 

 whorls with about four spiral ribs, tessellated by transverse 

 threads ; penultimate whorl with a stout medial ridge, two behind, 

 one at the posterior suture, and two or three in front. The ribs 

 are rounded, unequally disposed, incised by rather distant oblique 

 threads. 



Last whorl ventricose, with a round shoulder, posterior to 

 which are five spiral ribs, the medial one the strongest, the pos- 

 terior one margining the suture ; the ribs are crossed by sharp 

 threads which crenulate them, but on the middle of the whorl are 

 obsolete or continued as striae; base with a few encircling 

 depressed ribs. 



Aperture ovately lunate ; outer lip plain, reflected ; columella 

 nearly straight, medially thickened, twisted and obliquely trun- 

 cated at the end, with about ten slender revolving plaits, ex- 

 panded over the umbilical region. 



Dimensions. — ^Length, 25; breadth, 20; leng-th of aperture, 18. 



Locality.— JJ^^Qv beds at Muddy Creek. 



This species, which resembles in miniature >S'. nivea, Brazier, 

 but has a difierent ornament, is dedicated to Baron Sir F. von 

 Mueller as a public mark of recognition of his contributions to 

 the phytology of the Australian Tertiary Period. 



4. Semicassis trinodosa, spec. nov. Ptate vii. , fig. 12. 



Shell globosely ovate, spire short, acuminate, ending in a small 

 conical pullus of three smooth convex whorls. 



Whorls four, excluding pullus, convex, with depressed spiral 

 ridges and narrower sulci. 



Last whorl ventricose, contracted at the base, sculptured with 

 flatly rounded spiral ridges, and ornamented with three rows of 

 tubercles, one on the rounded shoulder of the whorl, the third at 

 about half way to the front, the second about midway between. 

 The tubercles on the posterior row are the largest, smaller in size 

 on the medial row, and somewhat inconspicuous on the anterior 

 row. 



Aperture lunate ; outer lip very much thickened and slightly 

 reflexed, ascending to the middle of penultimate whorl; margin 

 smooth, except a few obscure denticles at the front ; columella 

 somewhat patulous, smooth, dentately ridged on the margin. 



