414 



DR. A. H. COOKE ON THE 



serrations ; base straight : laterals witli one of the denticles (in 

 place of the 3rd or 4th) immensely exaggerated in size, and in- 

 clining inward, forming a separation between the two parts of the 

 tooth; the inner part is narrow, produced like the prow of a 

 boat, and carries 3-4 fine needle-like denticles or seiise close to 



Text-fiaure 11. 



Lateral and rliacliidian tootli oi MitraJJammicfera Reeve. 



the big denticle, while the tip is bare ; on the outer part small 

 denticles (about 9) mount up towards the big denticle ; they are 

 .set apart from one another, gradually diminishing and leaving 

 the external portion of the margin quite bare. 



In another specimen (also from Durban), the rhachidicm is 

 smaller and narrower, and has a rather thicker framework ; the 

 cusps are very irregular, 2, 3, or 4 in number, of various sizes 

 and dispositions in different I'ows : the laterals are very faintly 

 serrated just inside the big denticle, which, on one side only of 

 the whole radula,, is bifurcated (and in some cases trifurcated) 

 like a lobster's claw. 



2. M. inteHirata Reeve. Durban. Rhachidian 7-cusped, 

 cusps shaped as iw^flammigera, the 3 interior much the largest, the 

 central the shortest of the three; base narrow, nearly straight ; 

 upper margin slightly curved : in the laterals the big denticle is 

 rather longer than \r\ flammigera ; thei^e are 4-5 minute denticles 

 or serrfe on the interior part of the maxgin ; on the exterior side 

 of the big denticle are 7-8 small denticles, end of framework 

 bare*. 



Text-figure 12. 



Lateral and rliacliidiau tooth of 3fitra fretiosa Reeve, Durban. 



3. J/, pretiosa Reeve. Suez. Rhachidian 7-8-cusped, cusps 

 sharp and projecting far beyond the upper margin, the 4 interior 

 much the largest, all deeply rooted; base straight: laterals with 



* Since this description was written, Mr. Burnup, of Durban, wlio sent the speci- 

 mens to Prof. Gwatkin, lias assured me that the two species flammigera and 

 interlirata are concbologically identical. 



