CLIDASTES WESTII, N. SP.
A specimen of much interest in the University collection differs so markedly from the other forms represented by specimens, as also from the descriptions of the known species, that we are constrained to regard it as new. It was collected by Mr. C. H. Sternberg from the uppermost of the Niobrara beds, in the vicinity of the old town of Sheridan. The character of the associated invertebrate fossils seems to indicate a different geological horizon, either the Fox Hills group, or transition beds to that group. The specimen consists of a complete lower jaw, quadrate, portions of the skull, the larger part of the vertebral column, and the incomplete hind and fore paddles. The vertebrae preserved are in two series, the one, numbering thirty-three, continuous with the skull; the other, sixty-three in number, all chevron caudals. The terminal caudals preserved indicate that there were several more in life, perhaps five or ten; the first of the series was evidently among the first of those which bore chevrons. Altogether the tail may have had seventy-five chevron caudals. The lengths of the two series are respectively seventy-one and seventy-two inches. Assuming that there was the same number of precaudal vertebrae as in C. velox, the entire vertebral column would have measured in life fifteen feet and four inches. The lower jaw shows the skull to have been very nearly twenty-four inches in length, making, for the animal when alive, a length of seventeen and one-half feet. This is one of the largest species, and it is interesting to observe that the real size here, as usually elsewhere among fossil vertebrates, is less than supposed. It is doubtful whether there is a Clidastes known that exceeded twenty feet in length.
While the skeleton was only about one half longer than the specimen of C. velox described in the foregoing pages, or of about the same length as a very complete specimen of C. tortor in the museum, the proportions of the animal were very much stouter. The figures given in plate VI of the twenty-fifth, or eighteenth dorsal, vertebra will show the relations between length and breadth: it is upon these remarkably stout proportions, and the shape of the articular faces, as indicated by the figures and by the measurements appended, that the species is chiefly based. The articular surfaces of the basal caudal vertebrae are remarkably triangular in shape, with the angles rounded, and the sides of nearly equal length. This triangular shape is persistent for the first twenty of the series as they are preserved. The paddles, as shown in plates IV and V, show much stouter proportions than in either C. velox or C. tortor.
The species comes nearest to C. stenops Cope, but it seems hardly the same. It is, also, evidently allied to C. dispar Marsh. From these and other described species, the following, extracted from the original descriptions, will serve to show the differences, in comparison with the specimen of C. Westii.
C. dispar.
The articular faces in the cervicals are a broad transverse oval, faintly emarginated above for the neural canal. In the dorsals and lumbars the cup continues transverse, and the emargination is deeper, but in the anterior caudals the outline becomes a vertical oval. There appears to have been thirteen mandibular teeth.
| Length of axis with odontoid process | 32 lines | 100 |
| Width between diapophyses | 26.8 | 103 |
| Length from edge of cup to end of ball in eleventh vertebra | 25 | 100 |
| Width of ball | 14 | 56 |
| Depth of ball | 12 | 43 |
C. Wymani.
In the cervical vertebrae, the outline of the articular faces is transversely cordate. The centra of the anterior dorsals are elongate, and much constricted behind the diapophyses. In the anterior caudals, the articular faces are a broad vertical oval.
| Length of axis with odontoid process | 19 lines | 100 |
| Width between diapophyses | 17 | 89.4 |
| Width of ball | 8 | 42.1 |
| Depth of ball | 7 | 36.7 |
| Length of sixth cervical, without ball | 13 | 100 |
| Width of cup | 9 | 69.1 |
C. rex.
The cervical vertebrae have very broad, transversely oval faces, with indications of emargination. The dorsals are elongated, with transverse faces, and a distinct superior excavation for neural canal. The articular ends of the anterior caudals are vertically oval.
| Length of posterior cervical vertebrae | 44 mm | 100 |
| Vertical diameter of ball | 24 | 54.5 |
| Transverse diameter | 29.5 | 67 |
| Length of a dorsal vertebra | 52 |
C. stenops.
The anterior caudals possess wide diapophyses. Their articular faces are a vertical oval, a little contracted above, sometimes a straight outline. They present a peculiarly elongate form.
| Length of axis (alone) | 60 mm | 100 |
| Vertical diameter of ball | 27 | 45 |
| Transverse diameter of ball | 27 | 45 |
| Length of the mandible | 720 | 100 |
| Depth at coronoid process | 150 | 20.9 |
MEASUREMENTS OF CLIDASTES WESTII.
This species is named in memory of Judge E. P. West, lately deceased, to whom our Museum owes so much for his long, diligent and faithful labors in the collection and preparation of the geological material.
[Erratum]: P. 17, line 15, for “Edestosaurus,” read Clidastes, and in next line, strike out “Proc. Acad.” etc.
Notes and Descriptions of Syrphidae.
BY W. A. SNOW.
WITH [PLATE VII].
Among the insects obtained by Prof. F. H. Snow in a recent trip to Colorado, is an excellent representative collection of the Diptera. The material for the following notes on Syrphidae is chiefly drawn from this collection. That such a collection affords so many points of interest in this, one of the best studied families of North American Diptera, is an evidence of the rich field that is presented by this important and little-studied order of insects.