Notes on a Dredging Excursion off the Coast of Durham, 163 



culum, the flattened tentacles, the diminutive spot-hke eyes of 

 these beautiful and interesting creatures were also distinctly vi- 

 sible. The young shell is very thin, brittle, pellucid, brilliantly 

 glossy and of a pale amber colour, nipple-formed, and perfectly 

 resembles the nucleus or upper whorl of the adult individual, as 

 will be seen by referring to the accompanying plate. Those most 

 advanced in growth have two whorls, and are half an inch in 

 length by a quarter in width. 



There is an interesting circumstance connected with one of 

 the capsules which may give some idea of the time required to 

 mature the embryo of this animal. A Serpula overlies a consi- 

 derable portion of the flattened marginal rim, and must therefore 

 at least have grown the length it has attained from its first attach- 

 ment to the rim, about an inch, since the capsule was deposited. 

 The embryo therefore requires more time for its development than 

 a Serpula does to increase an inch in length. 



Ova-capsules of Fusus Turtoni. Plate X. fig. 9. 



The ova-capsules of F. Turtoni were fished up off the North- 

 umberland coast last June. Three were obtained; two were at- 

 tached to the inside of a valve of Modiola vulgaris j and one to the 

 outside of another valve of the same species. They differ com- 

 pletely from those of F. Norvegicus^ in shape, in being double, in 

 number of embryos, and in mode of attachment ; but agree with 

 them in being solitary. They are ovate, compressed, lentiform, 

 and are supported on a short flattened peduncle. This peduncle 

 is a production of part of the margin of the capsule, and is consi- 

 derably spread at its base over the surface to which it is attached. 

 The capsule is composed of an inner and an outer case ; the latter 

 is of a pale yellow colour, opake, not very glossy, coriaceous, 

 and has a few raised lines across the upper surface ; the former 

 is very thin, and separated from the latter by a parallel, fibrous, 

 silky layer. One of the capsules is nearly an inch in greatest 

 diameter, and contains six embryos, the largest of which is half 

 an inch in length by one-fifth in width, and has three volutions 

 which perfectly resemble the apex of the mature individual. They 

 are almost cylindrical, coarse, opake, the last whorl faintly spi- 

 rally striated and of a reddish brown colour. 



From the above descriptions it is evident that these two forms 

 are specifically distinct from each other, and from those with which 

 they have been and are most likely to be confounded, viz. F. an- 

 tiquus and B. undatum. The spawn of F. Norvegicus cannot for 

 a moment be mistaken for that of F. antiquus, as the capsules of 

 the latter are only half an inch in diameter, and are very coarse 

 and corrugated, and piled one upon the other in a conical heapr 



IS* 



