E. W. Berry — An American Spirulirostra. 329 



total width, and with the usual vascular markings. The 

 central half of its ventral face gradually rises from the 

 general surface in front of the phragmocone until at its 

 anterior end it projects downward a distance twice as 

 great as the proostracum is thick. This broad central 

 keel is excavated to form a shallow arch, curving slightly 

 forward and downward as a continuation of the arched 

 dorsal part of the phragmocone, but there is no trace of 

 ventral or side walls or any vestiges of there ever having 

 been any septa. The anterior end of this squarish keel 

 is broken away below the anterior margin of the proostra- 

 cum as though in life it had continued forward a greater 

 or less distance beyond the dorsal rounded margin of the 

 proostracum as a sort of giadius or pen. 

 Dimensions : 



Total length, 5.1 cm. 



Distance from tip to center of ventral boss, 1.15 cm. 



Distance from the tip to the boss marking the initial chambers 

 of the phragmocone, 1.8 cm. 



Length of the phragmocone, 1.7 cm. 



Greatest diameter of the phragmocone, 6 mm. 



Greatest distance between the later formed septa, 1.5 mm. 



Length of proostracum, 2.6 cm. 



Maximum width of the proostracum, 1.1 cm. 



Maximum height of the rostrum in the region of the ventral 

 boss, 1.0 cm. 



The various features that I have attempted to describe 

 in the foregoing paragraphs are well brought out in the 

 accompanying dorsal, ventral, and lateral views 2 , and in 

 the two diagrammatical, partly sectional drawings. 



This species is clearly distinct from previously known 

 forms. From the best known of these, Spirulirostra bel- 

 lardi, it differs in being slightly larger, with less sharply 

 conical guard, its coiled early chambers, more flattened 

 and much larger proostracum, and in having the phrag- 

 mocone iniated as an internal protoconch some distance 

 in front of the ventral boss, and not ventrally from a 

 protoconch imbedded in this ventral boss. I am writing 

 in terms of the finished product, and it should be under- 

 stood that ontogenetically, the phragmocone preceded the 

 guard and proostracum in order of development. 



2 The two best of these I owe to the skill of G. S. Barkentine. 



