Stiulics on marini' Oslrucods ."?3.'i 



the shell has its greatest breadth at about the middle; its sides are evenly and uniformly cm-ved; 

 the anterior and the posterior ends are of about the same type, rather narrowly rounded. The 

 surface o f t h e s li (> 11 has numerous very striking and rather large pores, but has 

 practically no hairs at all. It is almost quite smooth, having small cavities only partly, at least 

 anteriorly, and with finely reticulate sculpture, especiall\- on the rostrum. Seen from 

 inside (figs. 2 and 5): Medial bristles: On the rostrum there is a rather distinct row of fairly 

 long bristles running obli(juely upwards and forwards. Most of these bristles are of about the 

 sanic type as is shown in fig. 4, in other words they are weakly bifurcated, the proximal part 

 on one side is fui'uished with rather powerful secondary spines, the distal part having short, 

 fine hairs. Some of these bristles are, however, more decidedly bifurcated, others are ((uite 

 simple; some are equipped with more powerfid spines, others are almost smooth. The ventral 

 ones are not attached to a verruciform swelling. This row continues into a very dense row of 

 bristles running a short distance along the dorsal edge of the rostral incisur, the bristles of 

 which become more and more short and more and more powerfully equipped the more posteriorly 

 they are fixed (cf. fig. 3 for the three posterior bristles in this row). Apart from this row of 

 bristles there are on the rostrum a moderate number of what seem to be for the greater part 

 simple and bare, short or rather long bristles, scattered both in front of and behind the row. 

 The two bristles near the inner margin of the rostral incisur arc rather short and powerful, and. 

 like the posterior bristles in the row on the rostrum, furnished with strong spines, fig. 3. Above 

 these, near the joining line, there is a single very small bristle; apart from these three there 

 are no bristles inside the incisur. On the list behind the incisur there is a dense row of long 

 bristles, of about the same type as is shown in fig. 4, and between these there are short, simple 

 bristles; this row of bristles becomes more and more sparse posteriorly, the bristles becoming at the 

 same time shorter and weaker, and even at a c[uarter of the way along the shell it practically ceases, 

 althcnigh a few short, simple bristles may be observed on the list along the whole posterior part 

 of the ventral margin of the shell. The posterior part of the list, inside of the posterior margin 

 of the shell (perhaps it does not constitute an imbroken continuation of the list along the 

 ventral margin of the shell; at any rate I did not succeed in observing any connection, cf. the 

 diagnosis of the sub-genus) is broad and has a dense row of about 30 — 40 rather long spine-like 

 formations, the exact shape and nature of which I have been unable to decide with certaint}' 

 on account of the lack of material. On the part between the list and the margin of the shell 

 there seem to be no bristles at all. On the rostrum the selvage is very narrow, extending only 

 very slightly beyond the margin of the shell; along the ventral side of the shell, on the other 

 hand, the selvage is very broad, and extends rather considerably beyond the margin of the 

 shell, especially along the posterior margin of the rostral incisur — the incisur is quite filled by 

 it — and along the anterior part of the ventral margin of the shell; it ends posteriorly at the 

 posterior corner of the shell. It has close, fine and uniform cro.ss-striation and is even or 

 practically even at the edge, with only a faint indication of an extremely fine serration. 



First antenna: — Third joint: The bristle on ti>e anterior side is attached near 

 the proximal boundary of the joint and is not quite as long as tlie anterior siile of this joint; 

 the postero-distal bristle is somewhat shorter. The anterior bristle of the fourth joint is not 



