68 PROCEEDINGS OF THE ACADEMY OF [1890. 



This species is separated from Murex tribulus Linn., l)y the first 

 whorl beina: not so compressed, the carina not so near the suture be- 

 h)\v, and in the terminal varix being low, inconspicuous and not 

 ti-ianirular. 



Murex tribulus, Linn. (Fig. ■'>). 



The nucleus consists of about one and a half glossy, horn-colored 

 whorls ; a carina begins at the apex and continues round the apical 

 whorl until it finally disappears in the sutui'e above the second 

 whorl ; the lateral outline of the first part of the whorl descends 

 outwardly in a straight slant to the 'carina, and from 

 the carina to the suture below it slants inward ; the 

 outward slant is three times the length of the inward 

 Fig 3. slant ; the lateral outline of the second part of the 

 whorl descends outwardly in a slight curve to the carina, and 

 from the carina to the suture below it slants inward. The carina is 

 situated but a short distance above the suture of the whorl below, 

 almost concealed by the following whorl. 



The apical whorl ends with a small thread-like varix ; from this 

 varix the wdiorls are nodulous until the spinose varices appear upon 

 the third whorl ; there are nine ribs to each whorl until the spinose 

 varices appear; the suture between the first and second whorls is a 

 little impressed. 



Separated from Murex occa Sowb., by the carina being nearer the 

 suture below and by the varix being slightly shouldered instead of 

 rounded as in occa. The lateral outline of the whorl is convex in 

 tribulus whilst in occa it is straight. 

 Murex rectirostris, Sowb. (Fig. 4). 



The embryonic nucleus consists of about one and one-fourth,, 

 smooth, polished, rounded whorls ; a carina begins after about one- 

 half a whorl, traverses the whorl in an oblique direction, and finally 

 runs into the lowest spiral line of the succeeding whorl ; the lateral 



A outline of the whorls shows a more or less rounded ap- 

 pearance ; the carina runs just above the suture of the 

 whorl below ; the top of the whorl is rounded. The 

 Fig. 4. last apical whorl ends with a distinct, well-devoloped, 

 horn-colored varix, succeeded by three rounded, high whorls of slow 

 increase, each crossed by about fourteen small, rounded ribs, and 

 having four spiral coi'ds ; the spinose varices appear upon the fifth 

 whorl ; the suture between the embryonic whorls is impressed. 



