360 ZOOLOGY. 



to the Zoological Garden of Rotterdam. It is noteworthy that these 

 species represent two sections of the genus, one of the sijecies of Gua- 

 deloupe (P. Qnoyana) and one of the eastern (P. Beyrichii) having no 

 umbilicus, while the other two, Pleurotomaria Adansoniana and P. 

 Bumpfii are deeply umbilicated. The soft parts of Fleurotomaria are 

 still unknown, although we may hope that our acquaintance with a form 

 so interesting may not be much longer deferred, inasmuch as a living 

 specimen of P. Quoyana was obtained by Professor Agassiz off the island 

 of Barbados (at a depth of 120 fathoms), and is now in the Museum of 

 Comparative Anatomy at Cambridge. (See Hilgendorf in Sitzungs- 

 berichte der Gesellschaft Naturf. Freunde zu Berlin, 1879, p. 72; Schep- 

 MAN in Tijdschrift Nederl. Dierkund. Vereen., vol. iv, 1879, p. 162; 

 Crosse & Fisher in Journal Couchyliologie, (3,) vol. xx, i^p. 203, 

 284, 1880.) 



DENTITION OF MARGINELLOID MOLLUSKS. 



The contour and development of the shell of Marginella is quite char- 

 acteristic, but nevertheless there are now known four distinct types of 

 dentition represented by forms jwssessiug decidedly similar shells, and 

 if the Eratoinaj are considered, we have a fifth. 



(1.) As is generally known, most of the species have a single central 

 tooth (o — 1 — o) with a narrow base, and this has been regarded as 

 being one of the distinctive marks of the family Marginellidw. 



(2.) A similar form, however, was shown a number of years ago, by 

 Stimpson, to have a single row of teeth peculiarly modified, resembling 

 those of theMuricinae, being thick, strong, and armed with many (7) den- 

 ticles, and was therefore differentiated by him as the type of a peculiar 

 fiimily — Cystiscidw. 



(3.) Towards the end of the year 1880 a third type was found to be 

 represented by what has been called Pseudomarginella UptopuSj and what 

 has been also by some (but erroneously) identified with the '■'■Marginella 

 glabella,''^ of Eastern Africa. Shells with their animals were sent from 

 Senegambia, and the species was ascertained to have the teeth arranged 

 in three long longitudinal rows, (1 — 1 — 1), and their form very similar 

 to that of the Buccinids, the lateral teeth being broad and armed with 

 three cusps. 



(4.) A fourth marginelliform type has also teeth in three series 

 (1 — 1 — 1), but the lateral teeth are slender and claw-like. The species 

 representing this has been described by Carriere as new under the 

 name Pseudomarginella 2)laty pus, and thus sj^stematically arranged with 

 the preceding, with which it is geographically associated. The difference 

 in dentition is, however, generally regarded as of family value. 



(5.) Still another marginelloid type, although much more diiferen- 

 tiated than any of the others, is represented by Erato, which is now 

 generally regarded as a true member of the family of C^yprieidi^e or Tri- 

 viidte. 



