52 
THE VOYAGE OF H.M.S. CHALLENGER. 
the young Erichthus are bordered with spines as in Alima, and the general structure of 
the larva is very Alima-like ; a resemblance which totally disappears in the older larvae. 
Habitat . — Common below low water mark on sandy beaches at Beaufort, N. C., 
U.S.A. 
Measurements. 
In hundredths 
of inch. 
In thousandths of 
total length. 
Large 
male. 
Large 
female. 
Large 
male. 
Large 
female. 
Total length on middle line from tip of rostrum to tip of telson, . 
2-41 
3-02 
... 
Rostrum, ....... 
•10 
T1 
•041 
■036 
Carapace, . . . . . . . 
•33 
•39 
•137 
•129 
Total length of carapace and rostrum, 
•43 
•50 
T78 
T65 
From posterior edge of carapace to posterior edge of second 
thoracic somite, ...... 
•04 
•12 
•017 
•039 
From posterior edge of second to posterior edge of third thoracic 
somite, ....... 
•10 
T4 
•041 
•046 
From posterior edge of third to posterior edge of fourth thoracic 
somite, ....... 
•13 
•17 
•054 
•056 
From posterior edge of fourth to posterior edge of fifth thoracic 
somite, ....... 
T6 
•20 
■066 
•073 
First abdominal somite, ..... 
•24 
•28 
TOO 
•092 
Second abdominal somite, ..... 
•25 
•29 
•104 
•095 
Third abdominal somite, 
•25 
•30 
T04 
•099 
Fourth abdominal somite, ..... 
•26 
•30 
•108 
•099 
Fifth abdominal somite, . . . . 
•25 
•30 
•104 
•099 
Sixth abdominal somite, ..... 
•13 
•18 
•054 
•059 
Telson, ....... 
T7 
•24 
•070 
•079 
Total length of hind body, .... 
1-98 
2-52 
•822 
•836 
Total length on. middle line, 
2-41 
3-02 
1-000 
L001 
Width of carapace at anterior end, .... 
•20 
•24 
•083 
•079 
Greatest width of carapace, ..... 
•30 
•33 
T25 
T09 
Width of second thoracic somite, .... 
•13 
•22 
•054 
•073 
Width of third thoracic somite, ..... 
•22 
•30 
•091 
•099 
Width of fourth thoracic somite, .... 
•24 
•32 
TOO 
T06 
Width of fifth thoracic somite, ..... 
•25 
•34 
T04 
•112 
Width of first abdominal somite, .... 
•31 
•45 
T29 
•149 
Width of second abdominal somite, .... 
•31 
•46 
T29 
T52 
Width of third abdominal somite, . . . 
•32 
•46 
T33 
•152 
Width of fourth abdominal somite, .... 
•32 
•46 
T33 
•152 
Width of fifth abdominal somite, .... 
•31 
•46 
T29 
T52 
Width of sixth abdominal somite, .... 
•26 
•34 
•108 
•112 
Greatest width of telson, ..... 
•29 
•36 
•120 
T19 
Length of first antenna from tip of rostrum to tip of longest 
flagellum, ....... 
•38 
•36 
T58 
•119 
Length of appendage of second antenna, 
•35 
T45 
Length of scale of second antenna, .... 
•08 
•12 
•032 
•04 
Length of eye, ....... 
•09 
•09 
•037 
•029 
Total length of swimmeret, ..... 
•38 
•42 
T58 
■139 
