CRUSTACEA MALACOSTRACA. III. 



our area, and of the large family Sphseromidse only two genera, each with a single species, have been 

 found. Most, and perhaps all, families or sub-families hitherto not met with within the "Ingolf" area 

 will never be found there, as they exclusively live in less cold areas, or belong to the sub-antarctic 

 or colder temperate parts of the southern hemisphere. 



In the following pages no less than 70 new species are described. Of these 4 belong to the 

 sub-order Flabellifera (sens. Caiman), 1 to the Valvifera and 4 to the Epicaridea, consequently 61 to 

 the sub-order Asellota. Three of the new Epicaridea are rather interesting, but it can be said that, 

 putting the sub-order Asellota aside, the material comprises only 59 species of the other four sub-orders 

 together, and most of these animals are well-known forms; though, of course, our knowledge of the 

 geographical and bathymetrical occurrence of the majority of these species is considerably expanded. 



But the material of the sub-order Asellota comprises 105 species, 61 of which are new. Tatter- 

 sall had only 32 species of Asellota from Great Britain and Ireland, G. O. Sars 35 species from Norway; 

 consequently the number of species from the "Ingolf" area is astonishing. The explanation is easily 

 given. Most of the Asellota are, like the majority of the rich family Tanaidae, deep-sea animals, as most 

 of them inhabit depths from 500 — 700 to 1870 fathoms. The majority of the deep-sea Isopoda hitherto 

 known from all seas together in reality belong to the Asellota, and in spite of the rich gatherings of 

 the "Ingolf it can safely be concluded that the warm area explored contains a good number of hitherto 

 undiscovered Asellota. Two reasons may be given, viz. that one of the two richest places was Stat. 

 36, 1435 fathoms, where 17 species of Asellota (two pelagic species not included) were found in less 

 than a liter of sifted bottom material, but the "Ingolf" has very few stations in the warm area with 

 depths from 1000 to 1870 fathoms; furthermore each of no less than 38 of my new species of 

 Asellota was found only at a single station. That the "Ingolf has gathered a material of deep-sea 

 Asellota which, in proportion to that secured by other deep-sea explorations, is extremely rich, is mainly 

 due to the method of collecting described in my report on the Tanaidacea, p. 3 (1913). 



B. Classification and Morphology. 



In his extremely valuable hand-book on the Crustacea (1909), Dr. W. T. Caiman wrote (p. 218): 

 "The structure of the Isopoda is so diversified, and the number of forms included in the Order is so 

 large, that their classification is a matter of some difficulty". This statement is true, but unfortunately 

 a long time must pass before it will be possible to propose a really satisfactory classification. Caiman 

 adopted, with some modifications, that proposed by G. O. Sars, and I adopt Caiman's classification with 

 a single additional alteration. But some remarks may be made here. 



As already stated, Caiman divided the order Isopoda into six sub-orders : Asellota, Phreatoicidea, 

 Flabellifera, Valvifera, Oniscoidea and Epicaridea. The result is that these sub-orders stand as equivalent, 

 but Caiman most correctly said that "they are of very unequal value", and pointed out some three 

 instances. The Asellota stand in reality rather apart from the rest; not only does the structure of their 

 pleopods isolate them, but they have preserved some primary features. The antennae have three joints 

 in the sympod and, generally, a distinct exopod, the squama, which frequently is movable; but among 

 other Isopoda an antennal praecoxa exists only in a few genera, and a squama is found only in Ligia 

 (see later on"). The coxse of the thoracic legs, except, generally, those of the first pair, are movable, and 



