test.m

NSFileManager *fileManager = [NSFileManager defaultManager];
NSArray *contents = [fileManager contentsOfDirectoryAtPath:directoryPath error:NULL];

NSEnumerator *e = [contents objectEnumerator];
NSString *filename;

while ((filename = [e nextObject])) {
    NSString *filePath = [directoryPath stringByAppendingPathComponent:filename];
    if ([[filePath pathExtension] isEqualToString:@"jpg"]) {
    // jpegitz
        [fileManager removeItemAtPath:filePath error:NULL];
    }
}