352 AXEL A. OLSSON 



men has the following dimensions: length 61 mm., height 18.8 mm., length 

 of pallial sinus from the posterior end 32.2 mm. 



Tagelns (Tagelus) irregularis, new subspecies Plate 62, figure 6 



The shell is larger than that of typical T. affinis, relatively thin, strongly 

 convex, often much distorted, the anterior and posterior umbonal slopes 

 more pronounced, the midzone of the disk often deeply impressed. Ihe 

 surface is white or stained rusty brown, the lines of growth coarse and 

 undulate, the periostracum thin, often worn off or left adhering only in 

 spots. The impression of the palHal sinus and the adductor scar is usually 

 deep. 



Length 80 mm., height 26.8 mm., diameter 20 mm., length of pallial 

 sinus from the posterior end about 42 mm. 



ITiis is a larger, thinner, and more inflated shell than typical T. affinis 

 It should perhaps be considered a distinct species but its somewhat irregular 

 shape may also be due to distortion and accidents of growth through living 

 amongst coarse cobbles. 



Range — Ecuador. Ecuador: Punta Montanita near Manglaralto. 



Tagelus (Tagelns) penianus (Dunker) Plate 62, figures 2-2b 



SUiquaria peruana Dunker, 1861, Proc. Zool. Soc, p. 426, No. 35. Hab. In littore 



Peruano (H. Cuming). 

 Solecurtus peruanus (Dunker), Reeve, 1874, Concli. Icon., vol. 19, Solecurtus, pi. 8, 



fig. 38. Hab. Turabez, Peru. 



Shell medium-sized, broadly rectangular, the ratio of the height to 

 length about 1 to 2.25, the beak and umbone nearly median, thin, moder- 

 ately convex, the surface of the disk somewhat depressed across the middle. 

 Posterior side rounded, the anterior somewhat obliquely subtruncate. Gen- 

 eral color white, the surface marked with coarse lines of growth, under a 

 thin, dull olive-brown periostracum. Substance of the shell is thin but the 

 adductor scars and pallial line show distinctly, the pallial sinus itself rather 

 large, wide, and reaching to the middle of the shell cavity. 



Length 41.5 mm., height 18.1 mm., diameter 12 mm. Old Panama. 



The shortest and highest species. Some loose valves from Bucaro have 

 a length of nearly 48 mm. 



Range — Panama southward to Peru. Panama: Old Panama; Bucaro. 

 Peru: Tumbez. 



Subgenus Mesopleura Conrad, 1867 



Type species by subsequent designation, Gardner, 1928, Mesopleura 

 (Solen) bidentata Spengler {:=zTagelus divisus Spengler). Recent, east 

 coast of the United States. 



Umbonal cavity with a short, thickened ray, generally colored violet 

 and showing through onto the surface of the umbone as a colored streak. 



Tagelus (Mesopleura) polltus (Carpenter) Plate 62, figures 7, 7a 



Solecurtus politus Carpenter, 1855, Cat. Mazatlan Sliells, Britisii Museum, p. 27, No. 38. 

 Tagelus {Mesopleura) politus (Carpenter) Hertlein and Strong, 1950, Zoologica, vol. 

 35, pt. 4, p. 224, pi. 1, figs. 8, 10. 



