484 STOMATOPODA. 



the presence of one enormously long frontal spine and two posterior spines. 

 The usual dorsal spine is absent. The tail plate is rounded and has the 

 character of the tail of a macrurous Zoaea, but in the young Zoaea the third 

 pair of maxillipeds is absent and the appendages generally have a brachyu- 

 rous character. A Megalopa stage is hardly represented, since the adult 

 may almost be regarded as a permanent Megalopa. 



Stomatopoda. The history of the larval forms of the Stomatopoda 

 (Squilla etc.) has not unfortunately been thoroughly worked out, but what is 

 known from the researches of Fritz Miiller (No. 495) and Claus (No. 494) is 

 of very great importance. There are it appears two types, both of which 

 used to be described as adult forms under the respective names Erichthus 

 and Alima. 



The youngest known Erichthus form is about two millimetres in length, 

 and has the characters of a modified Zoaea (fig. 226). The body is divided 

 into three regions, an anterior unsegmented region to which are attached 

 two pairs of antennas, mandibles, and maxillae (two pairs). This portion 

 has a dorsal shield covering the next or middle region, which consists of 

 five segments each with a pair of biramous appendages. These appendages 

 represent the five maxillipeds of the adult 1 . The portion of the body 

 behind this is without appendages. It consists of three short anterior 

 segments, the three posterior thoracic segments of the adult, and a long 

 unsegmented tail. The three footless thoracic segments are covered by the 

 dorsal shield. Both pairs of antennae are uniramous and comparatively 

 short. The mandibles, like those of Phyllopods, are without palps, and the 

 two following pairs of maxillae are small. The five maxillipeds have the 

 characters of normal biramous Zoaea feet. From the front of the head 

 spring a pair of compound eyes with short stalks, which grow longer 

 in the succeeding stages ; between them is a median eye. The dorsal 

 shield is attached just behind this eye, and is provided, as in the typical 

 Zoaea, with a frontal spike while its hinder border is produced into two 

 lateral spikes and one median. In a larva of about three millimetres a pair 

 of biramous appendages arises behind the three footless thoracic segments. 

 It is the anterior pair of ab- 

 dominal feet (fig. 226). The 

 inner ramus of the second pair 

 of maxillipeds soon grows 

 greatly in length, indicating 

 its subsequent larger size and 

 prehensile form (fig. 227 g). 

 When the larva after one or 

 two moults attains a length FlG - "6. SECOND STAGE OF ERICHTHUS 



of six millimetres (fie 227) LARVA OF SQUII.LA WITH FIVE MAXILLIPEDS AND 



(tig. 227) THE FIRST PAIR OF ABDOMINAL APPENDAGES. 



the abdomen has six segments (From Claus.) 



1 These five maxillipeds correspond with the three maxillipeds and two anterior 

 ambulatory appendages of the Decapoda. 



