254 BULLETIN 93, UNITED STATES NATIONAL MUSEUM. 



I have seen two apparently typical specimens, said to be West 

 Indian, one from " St. Crux, Doctor Griffith, I. Lea collection," the 

 other from St. Thomas, R. Swift, in the collection of the Academy of 

 Natural Sciences, Philadelphia. As both were associated in trays 

 with ordinary West Indian stalactifera, it seems possible that there 

 has been a mixture or exchange of specimens in the 50 years or 

 more they have been in collections. Without further evidence I hesi- 

 tate to add West Indies to the range of the subspecies, as its known 

 habitat is the Red Sea and East Africa. 



A single large example from Prison Island, Zanzibar, collected by 

 Sir Charles Eliot, 1901, is in the collection of the Academy of Natural 

 Sciences. It differs from the Aden examples by having the oper- 

 cular valves white within. The scutum is wider, with a deeper and 

 wider articular furrow. The tergum has the angle between basal 

 margin and spur less deeply entering, and the scutal margin is 

 broadly inflected below (pi. 58, figs. 6, Ga). 



TETRACLITA SQUAMOSA STALACTIFERA (Lamarck). 



Plate 59, figs. 1 to 5&. 



1818. Balamis stalactiferus LAMARCK, Animaiix sans Vertebres, vol. 5, p. 



394 (Habite les mers de St. Domingue). 

 1854. Tetraclita porom var. communis DARWIN, Monograph, p. 329, pi. 10, 



fig. la (? and It, Ifc). 

 1854. Tetraclita porosa var. nigrescens DARWIN, Monograph, p. 329, pi. 10, 



fig. 16. 



Type. Presumably in Musee d'Histoire Natural de Geneve, from 

 the island of Haiti. 



Distribution. West Indies and American mainland, Florida to 

 southern Brazil ; west coast of Mexico. 



The surface is typically eroded, dull, and variable in color, dirty 

 white, cream, pale olive-buff, or plumbeous-black, the sheath 

 plumbeous-black (never green or pink even in forms externally 

 light colored). Pores larger and fewer, in the average, than in T. s. 

 squamosa or T. s. rufotincta. Usual diameter of adults from 24 to 

 30 mm. 



The scutum is dusky slate-violet, dull violet-black, or raisin black 

 or clouded with these colors internally, with paler or whitish bord- 



