560 Transactions of the Society. 



2. D. eaudata is described as having a smooth ridge or keel running 

 along the dorsal surface of the broad part of the body, apparently along 

 its whole length. The new species has this ridge confined to the distal 

 half of the broad part. 



3. No reference is made to the small knobs at the end of the foot, 

 one or more of which are always present in the new species. 



In various other points the language is hardly that which would 

 naturally be used in describing the Port Royal species, but the above 

 are, I think, sufficient. 



Description of the new species. The body expands posteriorly, and 

 terminates in a large foot-like prominence, the ventral edge of which is 

 in a line with the ventral edge of the rest of the body. This terminates 

 in one, two, or three, small knobs, or prominences. A smooth keel-like 

 ridge runs along the posterior half of the dorsal edge of the wide part 

 of the body. The funnel at the head is very large, larger, I think, than 

 in any other species. It is very nearly equal to the whole width of 

 the body. Its surface is wrinkled, not finely striated as in Saville 

 Kent's species. The collar, round the neck, posterior to this, is very 

 delicate and difficult to see; but its dorsal extremity is strengthened 

 by a thick and long projection of the cuirass. This projection is also 

 characteristic of the species. The ventral plates are three or four in 

 number, the fourth one being a small posterior one, as figured. The 

 first of these seems to be attached to the right valve of the cuirass, and 

 the second to the left valve. This latter plate is frequently more or 

 less veined with a network of approximately circular meshes. The 

 cuirass is extremely thick and is pierced with many holes, which at the 

 level of the surface are large, and form a complete network ; at a tower 

 level they terminate almost in a point. 



From its half keel I propose to call it D. semicarinata. Length 

 0"0036 in.; breadth of body 0'0016 in.; breadth, including ventral 

 plates, 0-0022 in. 



