139 



Gen. 37. WeStWOOdia, Dan;). L855. 



Syn: Pseudothalestris, \\r-.x\\. 

 Pseudowestwoodia. Scott. 



Generic Characters. Body short and stout, sub-pyriform in shape, with 

 the anterior segments more or less imbricate dorsally. Cephalic segment very 

 large and boldly vaulted above, rostral projection deflexed, not defined at the 

 base. Urosome comparatively small, attenuated. Caudal rami short and broad. 

 Eye well developed. Anterior antennae with the articulations more or less reduced 

 in number. Posterior antennae with the outer ramus of moderate size, 3-articu- 

 late. Oral parts differing somewhat in structure from those in the other Thale- 

 stridas. Anterior lip very prominent. Mandibles with the masticatory part nar- 

 rowly produced, palp well developed, with the basal part oblong in form, and 

 both rami short, the outer one abruptly reflexed and carrying long plumose setse. 

 Maxilla? with the masticatory lobe likewise considerably produced, and terminating 

 in a claw-like projection. Anterior maxillipeds short and stout, with a strong 

 incurved claw at the end, lateral lobes comparatively simple. Posterior maxil- 

 lipeds powerfully developed and of normal structure. 1st pair of legs with the 

 rami very unequal, the outer one being quite short and composed of only 2 joints, 

 which in some cases are confluent in one, inner ramus elongated, 3-articulate. 

 resembling in structure that in the genus T/m/rx/nx. Natatory legs normally 

 developed, having the proximal joints of the rami rather broad; inner ramus of 

 2nd pair of legs in male transformed, being only composed of 2 joints, the last 

 one more or less lamellar, with 2 unequal spines at the tip, and another issuing 

 near the base outside. Last pair of legs with the distal joint comparatively small, 

 proximal joint more or less lamellarly expanded inside; marginal setaa generally 

 much elongated. 



Remarks. This genus was established by Dana as early as the year 1855. 

 to include the form described by Baird as Ari.xn-tlrttx iioli'il'i*. The genus Pxctnlii- 

 ihalestris of Brady cannot in my opinion be supported, as the only distinguishing 

 character, the biarliculated structure of the outer ramus of the 1st pair of legs, 

 is also found in a species - - to be described below - - which so closely resembles 

 the type of the genus Westiwodia. that it may easily be confounded with it. As 

 to the systematic position of the present genus, the opinions of carcinologists have 

 been somewhat at variance. Boeck associated this genus with Jrfj/a in his sub- 

 family Idy'ma', on account of the narrowly-produced mandibles, whereas Prof. 

 Brady rightly removed it from that place, and included it in his subfamily I/nr- 

 which, however, contains forms referred in the present account to 4 



