402 Dr. W. T. Caiman on the 



.... in the largest specimen narrower than in the smaller 

 ones. Fig. 8 (pi. i.) represents one of the smaller ones." 

 The figure, however, measures 28 mm. in length of capitulum, 

 and as it is stated to be " magnified two diameters," it would 

 correspond exactly in this dimension with the largest of the 

 type-specimens. Its width represents an actual measurement 

 of 8*5 mm., which is considerably greater than that of any of 

 the specimens. It does not seem possible, therefore, to 

 identify this figure with any individual specimen, although 

 in the form of the scutum, and particularly in the angle 

 formed by its basal and occludent margins, it shows a certain 

 similarity to the second in point of size among the type- 

 specimens. This individual, of which the capitulum measures 

 9 mm. in length, is described separately below. 



The Museum also possesses* the remains of the specimen 

 described and figured by Gravel, as well as a number of 

 other specimens from the same locality (" off coast of Cuba ") 

 which were seen but not examined in detail by him (Gruvel, 

 t. c. p. 159). Some error has crept into Gruvel's measure- 

 ments of his specimen. Fie gives the length of capitulum as 

 14 mm. and its width as 4| mm., and his statement that it is 

 about three times as long as wide has been copied by Pilsbiy, 

 who regards this as the chief character distinguishing the 

 species from his M. subcarinatum. The statement, however, 

 is in conflict with Gruvel's own camera drawing of the outline 

 (/. c. pi. xvii. fig. 9) and with the specimen itself. When 

 the valves are placed together the capitulum measures about 

 13 mm. by 6 mm., a proportion which agrees well with 

 Gruvel's drawing. 



Description of Irlolotype. — Valves covered with a fine 

 nearly colourless cuticle, without seta?. Lines of growth 

 well-marked, with finer concentric ridges between; radial 

 striaticns very fine, but distinct. Scutum (fig. 1, A) twice as 

 h ng as wide, occludent margin convex, tergal margin 

 straight, carinal margin convex above, deeply concave below, 

 basal margin forming an even curve with occludent margin, 

 with the chord of which it makes a very obtuse angle ; basi- 

 carinal angle acute and recurved. Ridge from umbo to apix 

 well-marked, curved, distant from occludent margin except 

 near the ends ; ridge from umbo to carino-tergal angle low 

 and rounded but distinct. A small umbonal tooth on inner 

 suif'ace of both valves and a basal area which is radially and 



Unfortunately the history of these specimens is incomplete, and the 

 indications of locality and depth quoted by Gruvel fiouj the labels 

 Hied. 



