DENTALIUM. 103 



42. D. pseudo-sexagonum, Desk., f. 31. — Testa alba, tenui, 

 angusta, leviter arcuata' ; ad apicera et versus medium costis sex, 

 validis, deinde evanidis, medio et ad apertura marginem testa 

 striata ; apice integro. — Six-ribbed at or near the apex, thence to 

 the margin ribless, but finely striated. 



43. P. hexagonum, Gould, f. 10. — Testa alba, angusta, medi- 

 ocriter arcuata ; costis sex, acutis ; iuterstitiis planulatis ; apice 

 integro. — A regularly hexagonal shell, with distinct, sharp ribs at 

 the angles. 



44. D. sexcostatum, Sowb. T/i., f. 11. — Testa pallida, valide 

 arcuata ; costis sex, validis, rotundis ; iuterstitiis profundis, stria- 

 tis ; apice integro. — Similar in form and proportions to D. Java- 

 nicum, etc., but with six rounded ribs, with deep striated interstices. 



45. D. quixquangulatum, Forbes, f. 33. — Testa parva, alba, 

 acuminata, valide arcuata ; costis quinque, tenuibus ; iuterstitiis 

 planis ; apice integro ; margine aperturas obliquo. — -Very small, 

 sharp, and curved with six thread-like ribs, and the margin of the 

 aperture oblique. 



46. D. quadrapicale, Hanley, f. 61. — Testa alba, leviter ar- 

 cuata, versus marginem lata, longitudinaliter striata, ad apicem 

 quadricostata, prope apicem iuterstitiis unicostatis ; apice integro ; 

 margine aperturse obliquo. — Commencing at the apex with four 

 angles edged by sharp ribs, then between each of these, a little 

 way from the apex, having an intermediate rib, and losing them 

 all before they reach the middle of the shell, whence the remain- 

 der is finely striated. 



47. D. dispar, Sowb. TL, f. 37. — Testa hyalina, laevigata, alba, 

 versus apicem pallide subviridi ; ad apicem quadricostata, prope 

 apicem iuterstitiis unicostatis ; costis evanidis. — More glassy than 

 I), quadrapicale, and smooth, the disposition of the ribs at or near 

 the apex being the same. It is not so wide towards the aperture. 



48. D. quadrangulare, Sowb. Sen., f. 31. — Testa alba, parva, 

 subcylindracea, longitudinaliter striata, ad apicem et versus me- 

 dium quadrigona, deinde rotunda, apice obtuso, integro. — White, 

 small, striated, cylindrical, four-sided at the apical end, rounded at 

 the other. 



49. I). tetragoxum, Sowb. Sen., f. 21, 22. — Testa alba, elon- 

 gata, leviter arcuata, laevigata, versus aperturam rotunda, versus 

 apicem quadrigona ; angulis acuticostatis ; apice integro. — White, 

 long and narrow, slightly curved, smooth, rounded towards the 

 aperture, four-sided near and at the apex, the angles being sharp- 

 ened bv distinct, thin ribs. 



