ISOPODS OF NORTH AMEEICA. 



17 



The first three free seo-ineiits of the thorax are \sul)equal; taken 

 together, somewhat shorter than the head and twice as long as the 

 foiu'th free segment. 



All the segments of the abdoiiuMi are pres- 

 ent and visible. The last segment is taper- 

 ing, wideh' rounded, and more than twice 

 as wide as long. 



The first pair of legs are robust; the 

 chelae are more than half as short as the 

 head; the fingers are a little shorter than the 

 hand, the thumb serrate almost to the apex. 

 The ambulator}^ legs are all subequal, slen- 

 der. The pleopoda are very short, and fur- 

 nished with a few short setas. 



The uropoda are very short, double- 

 branched, both branches being composed of 

 two articles, the inner branch being twice 

 as long as the outer branch, and stouter. 



The marsupium is composed of two large 

 lamelke issuing from the base of the fifth 

 pair of legs.*^ 



Fig. 20.— Cryptocope arctic a 

 (After Hansen), a, Antenn.e 



OF FEMALE, b, UROPOD OF FE- 

 MALE, c, Uropod of male. (I, 

 Anterior part of body of 

 MALE. (Enlarged.) 



4. Genus LEPTOGNATHIA Sars.'' 



Eyes wanting. Pleopods in female small and sometimes wanting; 

 those in male well developed. Abdomen composed of six segments. 

 Uropoda usually biramous, sometimes apparently simple, the outer 



«The above description is adapted from the following description of Hansen's: 

 Femiyia.— Corpus subcylindricum, circiter quadruplo et dimidio longius quam 

 latius. Scutum cephalothoracicum ad frontem versus sensim angustatum, margine 

 anteriore aliquantum producto et apice obtuse. Segmenta tria libera anteriora inter 

 se subsequalia, simul sumpta scuto cephalothoracico aliquanto breviora et segmento 

 quarto libero duplo longiora. Segmenta caudle omnia manifesta; segmentum ulti- 

 mum declive et valde rotundatum, plus duplo latius quam longius. Oculi nuUi. 

 Antennae primiparisquadriarticulatae, anguste conicse; scuto cephalothoracico quarta 

 parte breviores; articulus basalis duas quintas partes antennse explens, a latere visus 

 (;ylindricus, pronus ad basin versus sensim incrassatus; articulus secundus articulo 

 tertio plus quam dimidio longior et articulo quarto nonnihil brevior; articulus uterque 

 seta in angulo exteriore apicali instructus; apex articuli quarti .setis compluribus 

 longis ornatus. Antennse secundi paris tenues, quinque-articulata', antennis primi 

 paris nonnihil breviores. Pedes primi paris (chelipedes) robusti; chela scuto ceph- 

 alothoracico plus quam dimidio brevior; digiti manu paulo breviores, pollice prope 

 apicem serrato. Pedes gressorii omnes inter se suba^quales, tenues. Pleopoda bre- 

 vissima, setis nonnullis brevioribus instructa. Uropoda brevissima, biramea, ramis 

 ambobus biarticulatis, ramo internoquam externo duplo longiore et crassiore. Mar- 

 supium e laminis duabus magnis, ad pedes quinti jjaris affixis, formatum est. Long. 

 1.67 mm. — Hansen, Dijmphna-Togt. zool.-bot. Udb., 1887, p. 209. 

 '^ See Sars for characters of genus. 

 28589—05 2 



