284 UNDATED. 



TYPHIS. Montf. A genus composed of Murex tubifer, Auct. 

 and other similar species, which have the canal closed and a 

 perforated tube between each varix on the angulated part of the 

 whorls. Besides the fossil species originally described, there are 

 now five species known, which are figured in part 200, of the 

 Conchological Illustrations by the Author. Typhis tubifer, 

 fig. 397. 



ULTIMUS. Montf. {The last.) A genus composed of Ovulum 

 gibbosum, Auct. fig. 443, and other species in which the canals 

 are not distinctly defined, nor elongated. This fanciful name is 

 given to the genus on account of its being described in the last 

 page of the book. 



UMBILICATED. {Umbilicatus.) Having an umbilicus, as Nau- 

 tilus umbilicatus. 



UMBILICUS. {A navel) The hollow formed in spiral shells 

 when the inner side of the volutions do not join each other, so 

 that the axis is hollow. The umbilicus is marked with the letter 

 u in Helix algira, fig. 279. The term is also used to express any 

 small, neat, rounded hollow. 



UMBO. {The boss of a buckler or shield.) The point of a bivalve 

 shell above the hinge, which constitutes the apex or nucleus of 

 each valve, from which the longitudinal rays diverge, and the 

 lines of growth, commencing at the minutest circle, descend in 

 gradually enlarging concentric layers to the outer margin. The 

 umbones will be marked with the letter u } in Cytherea, fig. 117. 



UMBRELLA. {A little shade.) Fam. Semiphyllidiana, Lam. 

 Patelloidea, H\. — Descr. Patelliform, sub-orbicular, compressed, 

 rather irregular ; apex slightly raised, placed near the centre ; 

 margin acute ; internal surface with a central, callous, coloured 

 disc, surrounded by a continuous, irregular muscular impression. 

 — Obs. This genus is known from Patella, by its continuous 

 muscular impression. It is commonly called the Chinese Um- 

 brella shell. There are but two species at present known ; the 

 U. Mediterranea, and the U. Indica, fig. 233. 



UNDATED. (Unda, a wave.) Waved. 



