Usually the anterior three pairs are only reduced, and then redevelop side by side with the small posterior limbs as they appear. This larva is then termed the “Erichthus” (Fig. 100); but when they completely disappear the larva is called a “Pseudozoaea,” owing to its resemblance to the Zoaea stage of the Decapoda, which is also characterised by the suppressed development of the thoracic segments. [Illustration: FIG. 100.—Older Erichthus larva, with six pairs of abdominal appendages, × 15. (From Balfour, after Claus.) ] The so-called “Alima” larva of _Squilla_ is also a Pseudozoaea, but it is apparently arrived at directly without the previous formation and degeneration of the anterior thoracic limbs, the larva hatching out from the egg in the Pseudozoaeal stage. =Fam. Squillidae.=—Of the six known genera none extend into the cold subarctic seas; the majority are characteristic of the warm or tropical seas (_Gonodactylus_), some of the species having very wide ranges, _e.g._ _G. chiragra_, which is completely circumtropical, and appears to have entered the Mediterranean at some period, though it is very rare there. CHAPTER VI CRUSTACEA (_CONTINUED_)—EUMALACOSTRACA (_CONTINUED_): EUCARIDA— EUPHAUSIACEA—COMPOUND EYES—DECAPODA DIVISION 4. EUCARIDA. The carapace fuses with all the thoracic segments. The eyes are pedunculate. The mandible is without a lacinia mobilis. There are no oostegites, the eggs being attached to the endopodites of the pleopods. The hepatic caeca are much ramified, the heart is abbreviated and saccular, the spermatozoa are spherical with radiating pseudopodia, and development is typically attended by a complicated larval metamorphosis. =Order I. Euphausiacea.= [Illustration: FIG. 101.—Calyptopis larva of _Euphausia pellucida_, × about 20. _A.1_, 1st antenna; _Ab.6_, 6th abdominal segment; _E_, eye; _M_, maxillipede. (After Sars.) ] The =Euphausiidae=[116] agree with the Decapoda in passing through a complicated larval metamorphosis. The young hatch out as Nauplii, with uniramous first antennae and biramous second antennae and mandibles. In the next stage, or “Calyptopis” (Fig. 101), which corresponds exactly to the Zoaea of the Decapoda, two pairs of maxillae and a pair of biramous maxillipedes are added; the hinder thoracic segments are undifferentiated, but the abdomen is fully segmented, and the rudiments of the sixth pair of pleopods are already visible.