190 CALIFORNIA ACADEMY OF SCIENCES. 



slender; dactyls short, with n subterniiual spine. Postero-lateral angle of 

 the sixth abdominal segment acute, that of the two preceding segments 

 subacnte. Telsou tapering, roxiuded at the tip, and armed on the convex 

 dorsal surface with two pairs of spinules. 



Color iu life a dark purple. 



Length of body, 19 mm.; of carapace, 6 mm.; of hand, 6 mm. 



Catalina Island (Lockington)! Santa Barbara (Kings- 

 ley); Point Arena! 



This species is found under the mantle of the Aba- 

 lone, Haliotis rufescens, but it is not confined to that 

 habitat, for I found several specimens upon some sea- 

 urchiiis that were brought up from several feet of water 

 at Catalina Island. Their color was a dark purple like 

 the specimens described by Lockington and resembled 

 the color of the sea-urchins in whose spines they were 

 entangled when captured. At Point Arena I captured 

 from under a rock at low tide a single specimen, which 

 was nearly white. 



Alpheus (Betaeus) longidactylus (Lock.). 



Betceus longidactylus LOCKINGTON, Proc. Gal. Acad. Sci., Vol. VII, 1877, 



p. 35; Ann. Nat. Hist. (5), Vol. I, 1878, p. 480. 

 Alpheus longidactylus KISGSLEY, Bull. U. S. Geol. Sur., Vol. IV, No. 1, 



1878, p. 198; Bull. Essex lust., Vol. X, 1878, p. 58; Ibid., Vol. XIV, 



1883, p. 124. 



Carapace quite strongly compressed and smooth, with no trace of a ros- 

 trum or ocular spines, and scarcely notched at the center. No spines or 

 teeth on the anterior margin of the carapace. Basal spine of the anten- 

 nules slender, elongated, about reaching the tip of the second joint; last 

 two basal joints subequal; inner flagellum a little longer than the carapace, 

 the outer one considerably shorter than the inner and contracted near the 

 middle, the terminal portion slender. Antennae with a spine at the infero- 

 distal angle of the second basal joint; scale with a prominent terminal 

 spine which nearly reaches the tip of the peduncle, the latter reaching 

 about as far forward as the peduncle of the antennules. Maxillipeds 

 nearly reaching the tip of the autennal peduncle. Chelipeds elongated, 

 similar; merus with rounded angles, the distal end widened, the outer 

 surface with a broad, oblique sulcus; a short, transverse groove at the 



