24 THE VOYAGE OF H.M.S. CHALLENGEE. 



while the genus Squilla is restricted by him to those species which, with a similar 

 raptorial claw, have longitudinal carinse on the carapace and hind body ; the eyes not 

 constricted at the tips ; the carapace elongated, and the appendages of the thoracic 

 limbs slender and styliform. 



The forms which he includes in the genus CldorideUa are certainly less specialised 

 than the higher Squills, but the Challenger collections show that they are connected 

 with the latter by intermediate forms in such a way that it is impossible to draw a line 

 between them, and that they do not form two divergent branches, but a single series. 

 Squilla lata, n. sp. (PI. III. figs. 1, 2, 3), is a Squilla, according to Miers's definition, 

 while Sqtdlla chlorida, n. sp. (PI. II. figs. 1-5), is a CldorideUa, but Squilla fasciata 

 (PL III. figs. 4, 5) is so very similar to both of these species that it is very hard to 

 distinguish from them, and it is intermediate between them in respect to the very 

 characteristics upon which Miers bases his genera. We must therefore enlarge the genus 

 Squilla to include the Cldoridellie. 



Ontogeny. — The Alima larva is one of the most sharply defined larval types, and we 

 have every reason to believe that all the larvae in this group pertain to closely related 

 adults. As one of them has been kept by Faxon in an aquarium until it changed into 

 a young Squilla, and as all the species of the genus Squilla agree with each other in 

 several features which are not united in any other adult Stomatopod ; the flatness of the 

 hind body, the small number of marginal spines on the dactyle, the great number of 

 secondary spines on the telson between the intermediate and the submedian marginal 

 spines, and the greater length of the inner one of the two spines on the basal prolongation 

 of the uropod ; and as all the Alima larvae, including Alimericlithus, agree with each 

 other, and diflTer from all other Erichthidse except the anomalous Erichthalima, in 

 similar features, we can state with confidence that all Alima larvae are young Squills, 

 and that all Squilla larvae are Alimx. 



While the Alima is a highly specialised larva it is, in a certain sense, embryonic, for 

 the fully grown Alima closely resembles the young Lysioerichthus larva, as may be 

 seen by comparing fig. 4 of PI. I. with fig. 5 of PI. XII. The Erichthus, in some 

 cases and probably always, hatches from the egg as an Erichthoidina, while it is 

 probable that all the Alimse leave the egg in the Alima stage ; but this is so similar to 

 the young Erichthus that Glaus was disposed to regard his Erichthus multispinosus as 

 an Alima, although the fully growii Erichthus is very difi"erent from the Alima at any 

 stage of its development. Apparently the stage which the Lysioerichthus passes 

 through, immediately after the Erichthoidina stage, has proved to be so well adapted to 

 the needs of the Sqidlla larva that it has been lengthened at both ends of the larval 

 life until both the initial Erichthoidina stage and the final Squillerichthus stage have 

 been crowded out of its larval life, and the Alima hatches as an Alima and remains an 

 Alima until it changes into a Squilla. 



