W. C. M'lntosh on Linotrypame apogon. 



369 



L. — Note on Linotrypane apogon. By W. C. M'Intosh. 



To the Editors of the Annals and Magazine of Watnral History. 



Gentlemen, 



In the 'Annals' for this month (October) is mentioned an 

 article, by M. Edmond Perrier, "On a new intermediate Type 

 of the Subkingdom Vermes (Polygordius?, Schneider)." So 

 far as can be seen, this form is very closely allied to, if not 

 identical with, that previously described in the ' Proceedings 

 of the Royal Society of Edinburgh' (1873-74, vol. viii. p. 386), 

 from specimens dredged in abundance in the shell-gravel of 

 Bressay Sound, Shetland, in 1871. JVL Perrier classifies it 

 with Polygordius, as an intermediate type between the Anne- 

 lids and the Nemerteans. From the structure of the preserved 

 examples formerly alluded to, it was provisionally associated 

 with the Opheliidas, and named Linotrypane apogon. The 

 accompanying outlines (A and B) will explain the general 



structure of the body- wall, and supplement the description in 

 the ' Proc. Royal Soc. Edinb.,' since there was no opportunity 

 for the illustration of that paper otherwise than by the coloured 

 drawings at the reading of it. 



If the oblique muscle (m) in Linotrypane (fig. A), passing 

 upwards on each side, be greatly strengthened, the upper region 

 of the body will be drawn inwards and downwards, whilst a 

 ventral ridge (bounded superiorly by the oblique muscle) will 

 be formed at each side. This is just what happens in a new 

 Ammotrypane from Connemara (fig. B), in another from Kil- 

 libegs Harbour, and a third (noticed in the former paper) from 

 Valentia. The great oblique muscle springs in each case 

 from the raphe at the nerve-cords, and passes upwards and 

 outwards to the body-wall. Moreover, between the extremes 

 of structure (as shown in Linotrypane on the one hand, and 

 Ophelia limacina with its two prominent ventral ridges, or 

 Ammotrypane aulogastev with its single basal and two terminal 



Ann. & Mag. N. Hist. Ser. 4. Vol. xvi. 26 



