210 AXEL A. OLSSON 



Luclna (Pleuroluclna) leacocymoldes (Lowe) 



Phacoides (Pleuroluclna) leucocymoides Lowe, 1935, Trans. San Diego Soc. Nat. Hist, 



vol. 8, No. 6, p. 17, pi. 1, fig. 4. 

 Lucina (Pleuroluclna) leucocymoides (Lowe), Hertlein and Strong, 1946, Zoologica, vol. 



31, pt. 3, pp. 116, 117. 



Shell small, solid, its surface ornamented by a single, large radial rib 

 which occupied the middle half of the disk and is bordered on each side 

 by a deep groove or channel, the whole overrun by reflexed concentric 

 lirae. Lunule large, cordate, and equally divided between the valves. Hinge 

 strong with two cardinal teeth and divided laterals. Ventral margin strongly 

 crenulated. Average height of a shell about 20 mm. 



According to Hertlein and Strong, the species occurs as a Pleistocene 

 fossil on Albemarle Island, Galapagos. 



Range — Gulf of California south to Manzanillo and Tres Marias Islands, 

 Mexico. 



Subgenus CATILDfGA Chavan, 1937 



Type species by original designation, Chavan, 1937, Lucina trisulcata 

 Conrad. East coast of United States. 



Shell small, trigonal, rounded, more or less inequilateral, the anterior 

 side generally longer. Dorsal areas feeble to subobsolete. Hinge well de- 

 veloped, with two cardinal and lateral teeth in each valve. Surface marked 

 principally with fine concentric threads, often interrupted by resting sulci 

 which divide the disk in ledge or steplike sections. Lunule deeply excavated, 

 placed below the small, pointed beaks. Ventral margins crenulated. 



Key to Pacific Cavilinga 



I. Shell generally small (length 6 mm. or less). Valves strongly inequi- 

 lateral, the anterior side much longer, obliquely produced. 



L. prolongata 



II. Shell larger (13 mm., or more) nearly equilateral. 



1. Shell dosinoid, rounded. 



L. lampra 



2. Shell tongue-shaped, generally higher than long. 



L. linqualis 



Lucina (Cavilinga) prolonpata Carpenter Plate 31, figures 8, 8a, 10-lOb 



Lucina prolongata Carpenter, 1855, Cat. Mazatlan Shells, Brit. Mus., p. 100, No. 145 

 "Mazatlan". 



Shell small, irregularly trigonal, strongly inequilateral, the anterior 

 side is longer and obHquely produced, solid, depressed. Umbones wide and 

 prominent, ending in small, prosogyrate beaks curved over the large, con- 

 cave lunule. Surface sculptured by strong, rounded concentric threadlike 

 riblets, the disk divided into unequal segments by deep, resting sulci. Hinge 

 normal, the teeth well developed. Internal margins finely crenulated. 



Length 5.2 mm., height 5.5 mm., diameter of a right valve 1.75 mm. 



Length 7.7 mm., height 8 mm., diameter of a right valve 2.2 mm. 



