Cadulus colubridens is a tusk shell

Tusk shell

The tusk shells or scaphopods are a class of shelled marine mollusks. The scientific name of this class is Scaphopoda, meaning "shovel-footed". Shells of species within this class range from about 0.5 to 15 cm in length...

, or Scaphopoda, in the family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 Gadilidae

Gadilidae

Gadilidae is a family of tusk shells in the order Dentaliida.-Genera:* Bathycadulus Scarabino, 1995 * Cadulus Philippi, 1844* Dischides Jeffreys, 1867 * Gadila Gray, 1847* Polyschides Pilsbry & Sharp, 1898...

 of the order Dentaliida

Dentaliida

Dentaliida is one of the two orders of scaphopod mollusks, commonly known as elephant's tusk shells. The order Dentaliida contains most of the larger scaphopods.-Families:* Anulidentaliidae* Calliodentaliidae* Dentaliidae* Fustiariidae* Gadilidae...

, that has been described from only one specimen collected in 1874 by the H.M.S. Challenger

Challenger expedition

The Challenger expedition of 1872–76 was a scientific exercise that made many discoveries to lay the foundation of oceanography. The expedition was named after the mother vessel, HMS Challenger....

expedition. The original description and a drawing was published in 1879 by Robert Boog Watson

Robert Boog Watson

Robert Boog Watson was a Scottish malacologist and minister of the Free Church of Scotland best known as the author of the report on the Scaphopoda and Gastropoda collected by on the H.M.S. Challenger expedition to survey the world's oceans during the years 1873-1876. Watson also described...

, a Scottish

Scottish people

The Scottish people , or Scots, are a nation and ethnic group native to Scotland. Historically they emerged from an amalgamation of the Picts and Gaels, incorporating neighbouring Britons to the south as well as invading Germanic peoples such as the Anglo-Saxons and the Norse.In modern use,...

 malacologist

Malacology

Malacology is the branch of invertebrate zoology which deals with the study of the Mollusca , the second-largest phylum of animals in terms of described species after the arthropods. Mollusks include snails and slugs, clams, octopus and squid, and numerous other kinds, many of which have shells...

 who reported on the Scaphopoda and Gastropoda

Gastropoda

The Gastropoda or gastropods, more commonly known as snails and slugs, are a large taxonomic class within the phylum Mollusca. The class Gastropoda includes snails and slugs of all kinds and all sizes from microscopic to quite large...

 of the expedition. The specimen was collected at a depth of about 1300 m in ocean waters east of North Island

North Island

The North Island is one of the two main islands of New Zealand, separated from the much less populous South Island by Cook Strait. The island is in area, making it the world's 14th-largest island...

, New Zealand.

The species is described as having a smooth, white shell, with a swelling below the anterior aperture

Aperture (mollusc)

The aperture is an opening in certain kinds of mollusc shells: it is the main opening of the shell, where part of the body of the animal emerges for locomotion, feeding, etc....

and a length of 15 mm.