GASTROCOPTA. 69 



intermediate character, making a division arbitrary. All were 

 taken at one spot on the rim of the crater, directly inland 

 from the head of Tagus Cove. 



Tower Island shells are rather small, 2.3 to 2.6 mm. long. 

 They are rather cylindric, the color corneous to light brown. 



In the crater of Daphne Island, north of Indefatigable, both 

 brown and corneous forms occur. The shape is rather cylin- 

 dric. The infraparietal tubercle and the interpalatal fold 

 are often absent : 2.95 x 1.25 mm. Others are smaller, 2.6 x 

 1.15 mm. 



On Kicker's Rock, off Chatham Island (PL 17, figs. 3, 4, 

 forma hrunnea) the shells resemble those of Daphne, reach- 

 ing a large size, up to length 3, diam. 1.2 mm., 5i/) whorls. 

 The form is subcylindric and the color brown. The infra- 

 parietal tubercle is lacking and the interpalatal fold often 

 absent. These two islands are arid breeding places of sea 

 birds, blue-footed boobies on Daphne, man-o'-war birds on 

 Kicker's Rock. The station of corneous and brown Gastro- 

 copta on the crater rim at Tagus Cove is similarly arid and 

 dusty. 



Small or very small brown shells with the apertural char- 

 acters of munita have been noticed from a moist spot back of 

 Villamil, Albemarle. They also occur on Chatham Island, 

 where there seem to be transitions to small cylindric forms of 

 clausa, as noticed under that species. 



Gastrocopta clausa (Reibisch). PI. 17, figs. 10-19. 



Vol. 24, p. 99. This species is not distinguishable from 0. 

 munita by any characters of shape, size or color, all being 

 variable in both species. The number of teeth also varies 

 somewhat, but I have found the only really distinctive char- 

 acter to be the presence of a well developed suhcolumellar, 

 tooth in G. clausa. G. munita has merely a sloping callus 

 below the columellar lamella, sometimes very weakly tuber- 

 cular, or there is none. In typical G. clausa there is a nodule 

 peripherad of the inner end of the parietal lamella (PI. 17, 

 fig. 12) not present in G. munita. 



Typically developed specimens of each, such as I figured in 



