I860.] MR.T. DAVIDSON ON JAMAICAN BRACHIOPODA. 10.3 



2. Argiope barrettiana, Dav. (PI. XII. fig. 3.) 



Shell small, somewhat pentagonal ; dorsal valve semicircular, 

 slightly indented in front ; hinge-line straight, as long as the entire 

 breadth of the shell, and forming acute angles at its junction with 

 the lateral margins of the valves ; hinge-area narrow; valves unequally 

 convex, dorsal valve very slightly so and with a shallow depression 

 along the middle ; ventral valve very convex, with a deep sinus. 

 Surface ornamented with from eight to twelve corresponding radiating 

 rounded ribs, with interspaces of almost equal width, but of which one 

 is a little wider and deeper along the middle of each valve, while in 

 the sinus of the larger valve there sometimes exists a smaller or 

 shorter rib. Area in the ventral valve acutely triangular, foramen 

 large, deltidium rudimentary : shell punctate. In the interior of the 

 dorsal valve the apophysary system consists of a distinct loop or 

 riband-shaped lamella, originating at the base of the sockets, and 

 forming a curve on each side so as to meet and adhere to the single 

 central prominent submarginal septum, this lamella being also partly 

 confluent with the valve. Proportions variable ; the largest specimen 

 measured about 3 lines in length by a little more than 4 in width. 



This beautiful Argiope is of a light yellow colour, the interspaces 

 between the ribs being slightly tinged with red. It approaches most 

 nearly to Argiope cuneata (Risso), but is a much larger shell, and 

 possesses when full-grown a larger number of ribs. In external 

 shape it also bears some resemblance to certain examples of A. de- 

 collata, as well as to some other fossil species, but may be at once 

 distinguished by its loop, which is two- and not four-lobed. 



Hab. North-east coast of Jamaica, at a depth of about 150 fathoms. 



I have named this shell after my lamented friend Lucas Barrett, 

 whose life was so prematurely sacrificed to his zeal for scientific 

 discovery. 



3. Argiope woodwardiana, Dav. (PI. XII. fig. 4.) 



Shell very small, somewhat pentagonal, indented in front ; dorsal 

 valve semicircular ; hinge-line as long as the width of the shell, 

 moderately convex, but divided into two lobes by a deep median 

 sulcus ; ventral valve deeper and more convex than the opposite one, 

 and with a longitudinal groove along the middle ; beak very promi- 

 nent ; area acutely triangular, foramen large, deltidium rudimentary. 

 External surface smooth, whitish yellow, with a few red patches 

 arranged in radiating interrupted lines from the beaks. The shell 

 is also marked with numerous concentric lines of growth. In the 

 interior of the dorsal valve the loop is two-lobed, adhering to a 

 central submarginal elevated septum. Shell-structure punctate. 

 Proportions variable ; the largest specimen measured, length 2^-, 

 breadth 2, depth 1| lines. 



This interesting stout little shell differs from its congeners in its 

 shape as well as in its smooth and spotted surface. It was also 

 found alive by the late Lucas Barrett, at a depth of GO fathoms, on 

 the north-east coast of Jamaica, and is a much smaller shell than 



