THE MOTHER LOBSTER 193 
Savigny’s fine folio plate its characteristics are beautifully 
delineated. The enormously broad ultimate and antepen- 
ultimate joints of the second antennz will astonish and 
perplex any one who for the first time becomes acquainted 
with a crustacean of this family. In the present species 
the quadrangular rostrum, the little eyes very wide apart, 
and implanted at a little distance from the sharp anterior 
angles of the great oblong tuberculate carapace, the com- 
parative smallness of the legs entirely unchelate, and the 
breadth of the tail-fan, are characters which will attract 
and deserve attention. 
Thenus, Leach, 1819, has still only the type species, 
Thenus orientulis (Fabricius), in which the carapace is 
broader than long, with a bilobed rostrum, and the eyes 
placed on visible stalks at its anterior angles. There are 
twenty-one pairs of branchie. 
Ibaicus, Leach, 1815, has the carapace much broader 
than long, deeply incised on the sides, with a bilobed 
rostrum, and the small eyes planted far from the front 
angles; the broad second antennz not very remote on 
their inner margins, the pairs of branchiz twenty-one or 
twenty-two. Species of this remarkable genus are dis- 
tributed all over the Eastern seas, but [bacus verdi, from 
St. Vincent, Cape Verde Islands, and also from Sambo- 
angan in the Philippines, is said to afford the only speci- 
mens of the genus taken elsewhere than along the Pacific 
coasts of Asia and the Australasian Islands. ‘ Hence,’ 
Spence Bate who instituted the species observes, ‘the 
similarity that it bears to Ibaccus incisus (Péron) is the 
more remarkable, and, judging by the several figures 
and descriptions published, the differences are slight, 
except in the character and number of the dentations that 
arm the margins of the carapace and antenne.’ He also 
calls attention to the thinning out of the sharp lateral 
margins to an extent equalling that of some of the 
Brachyura. Moreover, while the cervical groove, often so 
conspicuous in the Macrura, is here wanting, the lateral 
notches are greatly deepened, and widely separate the 
suborbital and hepatic regions from the branchial. As in 
