KONGL. SV. VET. AKADKMIKNS HANDLINGAK. HANI). 19. N:O 4. 123 



4. Var. agglutinans D'ORB. We retain this name, notwithstanding it is not pro- 

 perly applied in a group of forms through which this feature is so commonly distri- 

 buted. It comes near to the typical form, but its aperture beiny furnished with margi- 

 nal teeth which feature seems to be of some constancy - - there is a reason for 

 ranking it as a distinct variety. The tongue of the mouth is generally forked. It is 

 finely agglutinant (h. e. composed of finest chalkdebris) and attains on the chalk-bot- 

 tom a larger size than any other of these varieties. 



5. Var. pulckella D'ORB. On the experienced authority of Mr. BRADY we refer 

 to this variety all longitudinally plicated forms of Mil. seminulum. It may be, that 

 ihe designation of i>bicornisn WALK., should have the preference as older. Our form is 

 not a typical pulchella, but irregularly and scantely plicated, generally longuecked 

 and a little agglutinant. It is found very rarely in coralline-gravel. 



6. Var. Brogniartii D'ORB. A finestriated Mil. seminulum, usually of the same 

 shape as Mil. oblonya MONT. 



It would, no doubt, be more conformable to a natural arangement of the va- 

 rieties of this species to assign to the striated and ribbed forms a place under their 

 respective corresponding smooth forms; for it seems as if those varieties had origi- 

 nated directly from each of the principal smooth ones. Nevertheless we have provi- 

 sionnally brought together in our synoptical list of synonyms all striate and costate 

 forms under one head. 



Figg. 319 320: the typical or nearly typical Mil- seminulum somewhat aggluti- 

 nant; from the chalk-bottom. 



Figg. 321 329: pigmyforms and young of Mil. seminulum; from 0,07 to 0,20 

 mm. in length. 



Figg. 330 334: var. scapha D'ORB.; 330: endview; 331 : edgeview; 332: sideview; 

 the aperture resembling that of Mil. ringens; 333 334: transverse and longitudinal 

 sections of the same. 



Figg. 335 345: transitional forms to flat i>trianyulari&i> form (porcellaneous); from 

 chalk-ooze. 



Figg. 346 354: carinate forms of ttriangularisfl D'ORB.; slightly agglutinant, not 

 quite porcellaneous; from the coralline-gravel. 



Fig. 355: transverse section of triyonula, highly magnified; of porcellaneous lustre; 

 from the coralline-gravel. 



Figg. 35(j 358, tab. X: pulchdla with few and irregular folds, slightly agglu- 

 tinant; from the coralline-gravel. 



Figg. 359 360; the typical nagglutinans* D'ORB.; 360 shows the closely toothed 

 mouthedge and the produced forked tongue. 



