MUSEUM OF COMPArvATIVE ZOOLOGY. 53 



very pronounced umbilical rib coarsely nodulated, then three rows of small 

 spines which twist into the umbilicus, above which its walls are smooth, but 

 twisted so that the proper perforation is very small. The whole shell more- 

 over is covered with the lines of growth which rise into elegantly imbricated 

 scales, regular on the base, irregular on top, where they produce by their irreg- 

 ularity a shagreened effect. Aperture circular, thickened in the adult ; pearly 

 substance of the shell thick and solid. Alt. 7.5. Maj. diam. 9.0. Diam. of 

 aperture, 3.5 mm. 



Station 2, 805 fms. Station 60, off Havana, 480 fms. 



This may belong to the subgenus Arene H. & A. Adams. Contrary to the 

 ordinary experience, those from the deeper water are the darker and smaller 

 specimens. 



This shell is a perfect little gem. Words can give but little idea of its 

 beauty under a magnifier. 



Hanleyia tropicalis n. s 



Dall, Sol. Results Expl. Alaska, Art. IV. p. 101, Dec. 1878 (name only). 



Chiton about 10.0 mm. in length and 5.0 mm. in width, with the usual 

 characters of the genus, i. e. anterior valve with an unslit insertion plate, other 

 valves without even the plates ; back with an angle of about 90°. Girdle in 

 the dried specimens thin, narrow, covered with close-set, white, glassy, slender 

 spines (1.0-1.5 mm. in length) above, and below with similar but much shorter 

 ones. Anterior valve with a well-marked mucro from which proceed concen- 

 tric stria3 of growth, and in front of which the valve is a little concave ; sculp- 

 ture of little tessellated flattened nodules radiating from the mucro, above which 

 are irregularly distributed small opaque white pustular bubbles of shelly mat- 

 ter looking like attached grains of coral sand ; posterior valve smaller, flatter, 

 with similar sculpture, but the pustules take on a decidedly cylindrical shape 

 and are elongated, looking like the stalks of decapitated mushrooms ; this ar- 

 rangement is still more marked on the posterior lateral areas of the interme- 

 diate valves, the anterior lateral areas also exhibit it (less prominently), but 

 with an obliquely antero-posterior radiation, while the former have it more 

 entirely lateral from the mucrones ; dorsal areas with the tessellated sculpture 

 alone, arranged longitudinally. Color entirely white. 



Pourtales, Sand Key, 128 fms. 



This is the first known species of the group from the waters of the tropics, 

 and is entirely distinct in sculpture and appearance from the others. 



GENUS PLEUROTOMA Lam. 



ANCISTROSYRINX n. subg. 



Shell with the posterior surface of the whorls concave, with a broad deep 

 sinus, bordered externally by a pectinated elevated frill, directed backwards. 



