MARINE MOLLUSKS — MACGINITIE HI 



them doubtful, and there are two that are even more questionable. 

 There is one very questionable var. normale, and several others that 

 could as easily be assigned to one form as the other. 



Plate 11 depicts B. angulosum and its varieties. Figure 7 of plate 

 11 is of a small B. angulosum with the typical few but prominent 

 longitudinal ribs, a strong carina, and an angle about midway of the 

 last whorl. In figure 6 the ribs are strong, the carina is only a sugges- 

 tion, and the angle is slight. In figure 5 there is no carina, no angle, 

 and the ribs are much less prominent. In figure 4, which is midway 

 in shape between figures 5 and 6, there is no carina, and the ribs are 

 similar to those in figure 5. Specimens shown in figures 4 and 5 would 

 be classed as var. subcostatum, but figure 6 is midway between the 

 typical B. angulosum and var. subcostatum. 



Although it has only three strong cords and a very weak fourth 

 (the type has four and a weak fifth), the specimen in figure 11 could 

 be placed in var. transliralum without question. The specimen in 

 figure 12 has two strong cords and a weaker third, and the ribs are 

 stronger than in figure 11. The specimen shown in figure 13 has 

 strong ribs and only one spiral cord and is intermediate between 

 B. angulosum and var. transliratum. 



The specimens in figures 1 and 2 could be placed in var. normale 

 without hesitation. Figure 3 is of a var. normale with flatter whorls 

 and a less flaring mouth; the apparent longitudinal ribbing is ab- 

 normal — the result of injuries. 



The specimen in figure 8 is midway between var. normale and 

 var. subcostatum, having a somewhat flared mouth like var. normale and 

 weak ribs as in var. subcostatum. Its one cord, even though weak, 

 allies it with B. angulosum. The specimen in figure 9 has two fairly 

 strong cords, almost no ribbing on the last whorl, and no angle, 

 while the one in figure 10 has the heavier shell of B. avgulosum, the 

 flaring outer lip of var. normale, ribs more like those of var. subcostatum, 

 and two cords that suggest relationship with var. transliratum. 



After examining hundreds of specimens of this species and its varie- 

 ties, I believe that the subspecies subcostatum, transliratum, and 

 normale are only forms of B. angulosum. Certainly there is no more 

 variation in all these forms than there is in those of Thais lamellosa, 

 in which it has generally been conceded that the subspecies should be 

 dropped. 



The only two existing specimens of B. angulosum cnismatopleurum 

 Dall are pathological ones. The type specimen had been injured 

 several times, had made repairs, and continued growing. Tlie 

 resulting shell is a squat form that is heavier and has more prominent 

 ribs than typical forms of var. transliratum. The second specimen, 

 from between Cape Beaufort and Cape Lisburne, is also a var. 



