318 



shell has become attached to the surface of some marine body, for 

 the protection of its siphons, and, like the usual part of the valves, 

 the tube is coloured and covered with a thin periostracum. 



The two specimens in Mr. Cuming's collection are very different 

 in external appearance. In the larger one (figured in the ' Proceed- 

 ings,' 1852, Moll. pi. 15. f. 5) the valves after they become united are 

 expanded considerably, forming a large irregular-shaped shield ; and 

 then they extend suddenly behind into a tube which is separated from 

 the shield by an impressed line and the front bag-like projection fill- 

 ing up the gap between the front of the valves, which is irregularly 

 wrinkled and scattered with small rather prominent perforations, evi- 

 dently formed for the protection of the cylindrical tentacles on the 

 surface of the mantle ; and the edge of the expanded part of the base, 

 by which it is attached to the shell on which it lived, is furnished with 

 similar projecting perforations, often placed in pairs. The entire shell 

 is covered with a thin periostracum. The posterior tubular part of 

 the shell is marked with a succession of rings, showing the period- 

 ical interruption in its growth, the prominent longitudinal lines 

 on its outer surface being continued from one to the other, showing 

 that the siphons of the animal must be constantly becoming longer 

 and longer a3 the animal grows, and is marked also by four equi- 

 distant prominences on its edge, which give the tube its regular 

 subquadrangular appearance. 



In the smaller specimen, which was attached to a stone, the small 

 valves, as soon as they were united, seem to have expanded behind 

 and on the sides into a continuous subquadrangular tube, with scarcely 

 any projection in front of the valves ; there is a small tube arising 

 in front and behind the dorsal edge of the valves, and curled over 

 their back. There are only a few tubular projections on the left 

 side of the attached part of the shell, instead of the number found 

 on the front and sides of the other specimens. 



In both the specimens the interior surface of the cavity is quite 

 smooth and continuous, and entirely destitute of the definite line 

 which defines the form of the proper valves of the shell, and separates 

 them from the tube, which is always so distinctly marked in the 

 Aspergilla. 



The valves of the young shell appear to be rather unequal in size ; 

 that is to say, the apex of the right valves in both the species is situ- 

 ated rather under that of the left, as if the right valve were rather 

 the flattest and smallest ; but the difference is not verv defined. 



7. Note on the Eggs of the Frigate Bird and Crocodile 

 of Jamaica. By E. Cavendish Taylor, M.A. 



The eggs of the Frigate Bird (Freyata aquila), which I now ex- 

 hibit, were taken by my brother, Mr. J. C. Taylor, on the 1st of 

 January 1858, at Fonseca Bay, on the Pacific coast of the Republic of 

 Honduras. They are of a pure white colour, and measure 2| incites 

 in length by If in breadth. 



