MACROCERAMUS. 



striate, the later ones similar or smoothish ; last whorl rounded, 

 with a basal keel or none. The suture is either smooth or 

 crenate. The axis is slender and solid, straight or somewhat 

 twisted spirally. (Macroceramus, a long earthen vessel.) 



' Head somewhat bilobed ; tentacles four, the two on the 

 upper surface of the head bearing the eyes ; foot short, taper- 

 ing behind and simple ' ' ( Guilding) . 



Jaw highly arched, very thin, composed of many thin, nar- 

 row, slightly imbricating plates, converging toward the middle, 

 thereby causing the median plates to be shorter. 



Radula rather narrow, its width hardly one-fourth the 

 length; teeth arranged in v-shaped roivs; general shape of the 

 individual teeth as in Urocoptis (pi. 14, fig. 8, M. tenuipli- 

 catus var. swiftianus) . The central tooth is narrower than 

 the laterals, but still well developed, with a simple, obtuse 

 cusp. The side teeth are all of one type, and decrease very 

 slowly in size ; the broad inner cusp is emarginate or notched ; 

 the outer cusp is rounded and rather short. Near the outer 

 edge of the radula the teeth are more oblique. The basal- 

 plates are very indistinct. There are 27.1.27 teeth in M. sig- 

 natus, 28.1.28 in M. t. swiftianus. 



Soft anatomy otherwise unknown. 



Distribution: Eastern Cuba, Haiti, Porto Rico, and the 

 faunally similar islets eastward. Not in western Cuba or 

 Jamaica. 



Macroceramus stands well apart from all other genera of 

 Urocoptina, being apparently nearest to Anoma, which it re- 

 sembles in the incomplete peristorne and rapidly tapering 

 spire of the shell, and the general shape of the outer lateral 

 teeth, as well as in having very much smaller teeth than other 

 Urocoptincu, and a larger number of them. The teeth of the 

 central row are like those of Autocoptis. The notch in the 

 inner cusp of the lateral teeth probably indicates that that 

 cusp in Urocoptince is formed by the union of entocone and 

 mesocone, though in other genera of the subfamily no record 

 of its composite origin remains. Macroceramus resembles 

 Anoma, Spirostemma and Microceramus in the minute size of 

 the individual teeth. The teeth of equally small species of 



