94 DISCOVERY REPORTS 



Distribution. Antarctic: (i) Ross Sea area; (2) Margaret Bay, near Doumer Island, 

 Palmer Archipelago, and South Shetlands. 



Family AMMOTHEIDAE 



Genus Ammothea, Leach 



Ammothea, Leach, 1814, p. 33. Bouvier, 1913, p. 123. Caiman, 1915, p. 49. 

 Leionymphon, Mobius, 1902, p. 183. Hodgson, 1907, p. 39. 



The total number of specimens belonging to the genus Ammothea represents a small 

 percentage of the entire collection, yet no fewer than five new species, each with one or 

 two well-defined characters, are represented. Of these A. tetrapora is unique in having 

 four, instead of the usual two pairs of male genital openings. Two species have each 

 an eight-jointed palp as in the genus Achelia (see Bouvier, 1913, p. 122, key), but they 

 are of much larger size, and the high transverse body ridges characteristic of the genus 

 Ammothea are present. Two species, both of large size, retain the chelate chelophore in 

 the adult {A. gigantea and A. striata). 



The proboscis varies greatly in relative length and in shape from species to species. 

 As a rule it is straight, though much curved in A. striata, and either pyriform or sub- 

 cylindrical. In three different forms {A. Joiigispina, Fig. 51, A. sp..? and A. stylirostris. 

 Fig. 56) it is widest at the base, which is surrounded by a distinct collar, and then tapers 

 gradually to a rather narrow point,^ forming a long piercing organ or probe. A similar 

 type of proboscis is found in the genus Austroraptus, where it is much more abruptly 

 narrowed in the distal half. 



The definition of the genus given by Hodgson and earlier writers requires considerable 

 modification and enlargement. The chief characters of the genus are given below, 

 followed by a key to the determination of the Antarctic and sub-Antarctic species. 



Trunk rather compact, with distinct transverse body-ridges often greatly elevated in 

 the centre; lateral processes in contact or separated by intervals up to their own 

 diameter. Cephalon broad, neck very short or wanting; ocular tubercle situated a 

 short distance behind the anterior border; eyes present. 



Proboscis cylindrical, pyriform or gradually tapering distally (styliform). 



Chelophore chelate in immature specimens, usually, but not always, with reduced 

 chela in adult ; scape single-jointed. 



Palp eight- or nine-jointed. 



Oviger ten-jointed, without terminal claw; sometimes an irregular series of special 

 spines on the last four segments. In the male the seventh segment is very short, setose, 

 and much wider than the three terminal segments. 



Legs rather stout as a rule; second tibia usually the longest segment (the femur is 

 longest in A. gigantea, the first tibia in A. spinosa); tarsus very short; propodus usually 

 armed with a few stout spines on the proximal ventral margin ; auxiliaries present. The 

 genital apertures occur in the male on the two posterior pair of legs (on all four legs in 

 A. tetrapora); in the female on all the legs. 



''- This form is designated "styHform" in the key. 



