32 Prof. M'Intosh's Notes from the 



first set arises from a transverse ridge^ which, however, does 

 not pass externally below the line of the bristles as in 

 Thelepus. On the whole, the area covered by the branchise 

 is longer antero-posteriorly than in Thelepus. 



No more distinctive feature between Grymaa and Thelepus 

 exists than the great size of the setigerous process and the 

 length of the bristles. The first setigerous process occurs 

 on the second segment, aud it is slightly shorter than those 

 Avbich follow^whilst inthe region of the shields the processes 

 form long lamella? with slightly expanded tips set obliquely 

 like the blades of a series of oars, the ventral edges of 

 which are curved and split for the extended line of pale 

 golden bristles. Moreover, when the process is removed, a 

 distinct twist like the blade of a propeller occurs in all the 

 pencils of bristles, a condition closely connected with the 

 functions of the bristle-tufts. As in Thelepus, the seti- 

 gerous processes spring from the posterior part of each 

 segment, and are dorso-lateral in position. Two ranges of 

 bristles occur in each tuft, a longer and a shorter, the latter 

 alternating with the former. The longer bristles have 

 nearly cylindrical shafts inserted deeply in the tissues, but 

 they taper from the surface distally, so that where the uari'ow 

 Avings commence considerable diminution has occurred, 

 and they taper after a second expansion to very fine, hair- 

 like, curved points. The shorter forms are much more 

 slender, but they also taper to hair-like points and have 

 narrow wings. The dorsal edge of each fascicle is bounded 

 by three or four strong bristles without the intervening 

 shorter and more slender forms, whereas the ventral edge 

 has shorter and more slender forms. 



The number of bristle-tufts is about thirty-two, and the 

 region behind has only unciuigerous lamellpe. The posterior 

 bristles present a broad, almost flag-like wing. 



The first row of hooks commences opposite the fourth 

 bristle-tuft, that is, in a corresponding position to that of 

 T. iriserialls, though in the latter it is the third setigerous 

 process. The rows are somewhat shorter than iu Thelepus, 

 and they are sooner elevated on ridges, indeed at the eighth 

 or ninth a distinct lamella is apparent, and at the twenty- 

 fifth it forms a fan-shaped fiap with the single row of hooks 

 in a curved line on the anterior face of the edge. The first 

 row of hooks is distinguished by the apparent length of the 

 base, but this is due to its narrowness. The typical hook 

 lias two distinct teeth above the main fang, the posterior 

 outline is deeply indented, the anterior outline (below the 

 great lang^ has a peculiar stud which leaves it at an obtuse 



