190 A DESCRIPTIVE CATALOGUE OF THE 



the mouth of which often are found young individuals of the same species. The 

 lanthmidcs differ chiefly from Scalidce by the floating apparatus adapted to their 

 oceanic life. Between the shells there are some marked transitions, e. g. Reduzia 

 and the ribbed lanthina (lodina) exigua, Lam,, on one side, and Scala {lanthoscala) 

 incojispicua, Sow., S. concinna, Sow., &c., on the other. The Scalidce may be con- 

 sidered creeping lanthinidce. 



Several attempts have been made to divide the genus Scala into subgenera, but 

 as yet none have proved successful. In Cat. Yoldi, 1852, p. 48, I adopted the 

 following divisions: — 



AciONA, Leach, with the whorls separated. S. scalaris, L. 



Scala, Klein (Clathrus, Okeii), whorls not separated. 



Clathrus, Gray (Seal, au^tralis, Linn., and 8. g7~dnlandica, Perry), with flat sutures. 



CiRSOTREMA, Morch, is generally adopted as a genus on account of the crispate varices. 



AciRSA, Morch, Prod. Moll. Gronl. 185*r ; Adams' Gen. Supp. Chiefly founded on the want of 

 varices; this character is, however, very doubtful. Scala ochotenais, Midd., which evidently 

 is nearly specifically the same, has sometimes rather distinct ribs, and Scala wroblewskyi, 

 Morch {Scalaria borealis, Gould), is sometimes quite smooth. 



In the Genera of H. and A. Adams, Nov. 1853, p. 220, the following subgenera 

 are added : — 



Amcea, H. and A. Adams ; Scala tninuta, Bolt (Scala martinii, Wood.) 



The chief characters, rudimentary ribs and spiral strise, are not constant even 

 in the same species. If the spiral line proves of generic value, Scala gronlandica 

 would enter this genus chiefly, as Scala loveni, Mac Andr., considered by several 

 as a variety only, has spiniferous ribs like Amosa minuta. 



Opalia, H. and A. Adams, was established on species with a spiral basal ridge, 

 a character probably of less importance, as Scala lamellosa, Lam., and Scala australis, 

 Lam., scarcely can be congeneric. 



AcRiLLA, H. and A. Adams, Proc. Zool. Soc. 1860, p. 241. Type Scala acumi- 

 nata, Sowb. Shell turritelloid, ribs filiform. 



The geographical distribution of the Scalidae agrees in many respects with the 

 Corals, the number of species being largest in the tropical seas, chiefly on the 

 coral islands, and smallest towards the poles. 



Thus in the north polar region are only found four species : Scala gronlandica, 

 Perry, is circumpolar; in the sea of Greenland and Labrador is found besides this 

 species Scala (Acirsa) borealis, Beck {Sc. eschrichtii, Holb.), which is not found 

 recent on the European side of the Atlantic Ocean, but occurs fossil in Sweden 

 (Uddevalla), Ireland, &c. 



In the northern part of the Pacific Ocean is found, besides Scala gronlandica, 



