82 THE VOYAGE OF H.M.S. CHALLENGER. 



Although Claus decided that they are young LysiosquiUae they show their relationship 

 to the o-enus Squilla as distinguished from Lysiosquilla by the following characteristics, 

 all of which are shared by all fuUy-grown Alima larvae. The dactylus of the raptorial 

 claw has on its inner edge a small number of marginal spines, usually about five or six ; the 

 hind body is wide and flat, and the postero-lateral angles of the abdominal somites end 

 in acute spines. The outer edge of the proximal joint of the uropod is bordered by a 

 small number of spines, usually less than eight, and the inner one of the two spines on 

 the ventral process from the posterior edge of the basal joint of the uropod is longer 

 than the outer, and it has a tooth or lobe on its outer edge; and the telson has six 

 marginal spines with minute secondary spines between the submedians, and four or 

 more larger secondary spines between the submedian and the second or intermediate, 

 and usually a single one internal to the base of the third or lateral marginal spine. 

 While it is true that all of these characteristics are not exhibited by every adult Squilla, 

 there are no Stomatopods except those of this genus in which they are all united, and 

 they are all of them present in most Squillm and in all the AUmw. 



Joined to the fact that Faxon has reared a Squilla from an Alima, they indicate very 

 clearly that the Alimse are Squilla larvse, and as we know of no other type of larva 

 which can be referred to this genus, the present state of our knowledge indicates that all 

 Squilla} have Alima larvae. As it can be shown very conclusively that the Alima is an 

 Erichthus, which has become accelerated in development and has dropped its Erichthoi- 

 dina stage, and has become peculiarly adapted for a rapacious pelagic life, it is highly 

 improbable that this change has taken place more than once, and as I shall give reasons 

 for believing that it occurred very soon after the evolution of the genus Squilla, and that 

 the larva of the most primitive of the true Squillie is an Erichthus-like Alima, the con- 

 clusion that all the Alimie are Squilla larvae is warranted by the facts. The validity of 

 these general conclusions can be better estimated after reading the descriptions of the 

 larvae which follow, but these descriptions will be the more intelligible if an outline of the 

 generalizations to be drawn from them be kept in mind. 



The Alima larva is characterised by the great elongation of the body, the possession 

 of a flattened elongate! carapace, with the posterior median dorsal spine absent or rudi- 

 mentary, the elongated abdomen and usually several of the posterior thoracic somites 

 exposed behind the posterior edge of the carapace, by the very great elongation of the 

 region between the antennae and the labrum, and by the fact that the eyes and eye stalks 

 are usually exposed on the sides of the long slender rostrum. The carapace is narrow 

 and its width is usually one-third or one-fourth of its length, although its total length 

 makes a much smaller part of the total length of the body than it does in the Erichthus 

 larva, as its increased length is more than overbalanced by the great elongation of the 

 hind body. The older specimens of Alima are usually much larger than most of the 

 Erichthus larvag, and the inner one of the two spines which project backwards from the 



