xiv UEOCOPTID^:. 



greatest in those genera which are most highly specialized in 

 other characters, notably those of the radula. 



Coloration of the shell is not highly developed, except in 

 the brilliant and polychromatic arboreal genus Anoma. Other 

 Urocoptidtf are either white (Holospira, Apoma, Myckos- 

 toma) or some shade of brown or yellow, rarely with a brown 

 band (as in Urocoptis sauvalleana, etc.) ; a few Jamaican 

 species being rose-color or purple. 



Sculpture is not much diversified in Urocoptidcz, consisting 

 of subvertical or oblique rib-striae. In some forms these 

 become weak or wholly obsolete (Anoma, etc.) ; in others the 

 rib-striae are diminished in number and increased in size, as 

 in the ribbed species of Urocoptis. A further development 

 is seen in species in which the ribs are hollow, the mantle 

 expanding into each as it is formed, as in the marine Murices 

 and Tritons, subsequently building a floor over the hollow 

 space. Such ribs represent the acme of sculptural develop- 

 ment in Urocoptida, and occur in various unrelated phyla, 

 such as Holospira minima (vol. xv, pi. 24, f. 5, 6), Idio- 

 stemma imcata (xv, pi. 44, f. 32), Callonia (xv, pi. 48, f. 3, 

 6), Urocoptis ~blainiana and scalarina, and Brackypodella 

 pallida (vol. xvi, p. 84). The ribbed type of sculpture is 

 sometimes transformed to a smooth surface by degeneration 

 of the ribs, which become reduced to nodes at the suture 

 and base, and then disappear, as illustrated by various species 

 of Idiostemma (vol. xv, pi. 45, 46), and also by the Cuban 

 species of Macroceramus. No species of the family has de- 

 veloped spines or hairs, and very few show spiral sculpture, 

 though that is seen in some forms of Ccelocentrum. 



The axis of the shell in the Urocoptidce may be a simple 

 pillar, but it is usually more or less specialized by the pres- 

 ence of spiral or obliquely vertical sculpture. Spiral lamellae 

 may be superposed upon an axis which is either straight or 

 twisted, the pillar itself having a spiral trend. The number 

 of superposed lamellae varies from one to half a dozen. They 

 may be either short, confined to one or two whorls (Aniso- 

 spira), or extend throughout the length of the shell (Euca- 

 lodium s. str.) . Vertical sculpture consists primarily of rib- 



