Tlie Barrettia Beds of Jamaica. 511 



in aged specimens seems to have been frequently broken, presumably 

 })y battering of the waves, and very irregularly repaired by the 

 animal. This species seems to have generally grown singly and alone, 

 as I have only seen few with any trace of attachment of others to 

 their sides. 



Dimensions. — The largest example I saw measured about 2| feet 

 in length and 1 foot in diameter at the top. In such aged examples 

 as this the ornamentation of sides and top is nearly worn away, and 

 the shell much eroded. The smallest is quite an infantine specimen, 

 2 inches high, the top valve irregularly convex and oval in outline, 

 measuring 4 inches in longer and 3 inches in smaller diameter, the 

 living chamber rather over 1 inch in longer diameter. 



Woodward's original specimen has sixty-five moniliform rays, 

 but the number increases with age, and a specimen of mine 

 a foot in diameter has about ninety. Another small specimen has 

 sixty-nine or seventy rays. 



Locality. — Barrettia bed, Green Island, Jamaica. The type 

 specimen came from Back River, Portland Parish, East Jamaica. 

 Maestrichtian (?)• Several examples were collected at Green Island 

 in various stages of growth. 



Barrettia cf. nmUilirata Whitfield. PI. XVIII, Figs, la, h ; 



PI. XIX, Fig. 1 ; and PI. XX, Fig. 3. 

 1897. Bull. American Mus. Nat. History, vol. ix, p. 2-44, pis. xxxiii-xxxv. 



Since the top valve of this and other Barrettias was unknown to 

 Whitfield, it follows that his diagnosis of the species is incomplete. 

 Those in my collection which are identifiable with the above species 

 as regards their smaller size and the fact that in proportion to their 

 size they bear a much greater number of moniliform rays, fall into 

 three or more fairly distinct varieties as regards shape characters. 

 The species is a much smaller one than is B. monilifera, being more 

 slender and never attaining the clumsy irregularity of growth that 

 B. monilifera does. The varieties may be described as follows : — 



(a) Large examples with a long, often bent, very gradually 

 tapering lower valve and a rather convex upper valve. Height 

 12-14 inches, diameter at top 7 inches. Typical form (?). See 

 Plate XIX, Fig. 1 . Several examples were collected. 



(6) Slender, tapering rather gradually to the apex, the top valve 

 nearly or quite flat. Height of lower valve 11 inches, diameter 

 at top 5 inches. Several individuals seem to have grown together ; 

 the sides are often flattened, indicating where another individual 

 grew against it. Var. cycUndrica nov. See Plate XX, Fig. 3. Two 

 specimens, one figured and another sent to Professor Douville 

 in Paris. 



(c) Stumpy, conical, or almost mushroom-shaped, the top valve 

 convex and irregular, with a central raised apex. Height 4 inches, 

 diameter of top valve 6j inches. This form seems to have grown 

 singly and alone. Var. conica, nov. See Plate I, Figs, la, 6. 

 Two specimens collected, one figured. 



